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def bfs(graph, s, t, parent): # Return True if there is node that has not iterated. visited = [False] * len(graph) queue = [s] visited[s] = True while queue: u = queue.pop(0) for ind in range(len(graph[u])): if visited[ind] is False and graph[u][ind] > 0: queue.append(ind) visited[ind] = True parent[ind] = u return visited[t]
networking_flow
def mincut(graph, source, sink): parent = [-1] * (len(graph)) max_flow = 0 res = [] temp = [i[:] for i in graph] # Record original cut, copy. while bfs(graph, source, sink, parent): path_flow = float("Inf") s = sink while s != source: # Find the minimum value in select path path_flow = min(path_flow, graph[parent[s]][s]) s = parent[s] max_flow += path_flow v = sink while v != source: u = parent[v] graph[u][v] -= path_flow graph[v][u] += path_flow v = parent[v] for i in range(len(graph)): for j in range(len(graph[0])): if graph[i][j] == 0 and temp[i][j] > 0: res.append((i, j)) return res
networking_flow
def bfs(graph, s, t, parent): # Return True if there is node that has not iterated. visited = [False] * len(graph) queue = [] queue.append(s) visited[s] = True while queue: u = queue.pop(0) for ind in range(len(graph[u])): if visited[ind] is False and graph[u][ind] > 0: queue.append(ind) visited[ind] = True parent[ind] = u return visited[t]
networking_flow
def ford_fulkerson(graph, source, sink): # This array is filled by BFS and to store path parent = [-1] * (len(graph)) max_flow = 0 while bfs(graph, source, sink, parent): path_flow = float("Inf") s = sink while s != source: # Find the minimum value in select path path_flow = min(path_flow, graph[parent[s]][s]) s = parent[s] max_flow += path_flow v = sink while v != source: u = parent[v] graph[u][v] -= path_flow graph[v][u] += path_flow v = parent[v] return max_flow
networking_flow
def binary_search(a_list: list[int], item: int) -> bool: if len(a_list) == 0: return False midpoint = len(a_list) // 2 if a_list[midpoint] == item: return True if item < a_list[midpoint]: return binary_search(a_list[:midpoint], item) else: return binary_search(a_list[midpoint + 1 :], item)
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def simulated_annealing( search_prob, find_max: bool = True, max_x: float = math.inf, min_x: float = -math.inf, max_y: float = math.inf, min_y: float = -math.inf, visualization: bool = False, start_temperate: float = 100, rate_of_decrease: float = 0.01, threshold_temp: float = 1, ) -> Any: search_end = False current_state = search_prob current_temp = start_temperate scores = [] iterations = 0 best_state = None while not search_end: current_score = current_state.score() if best_state is None or current_score > best_state.score(): best_state = current_state scores.append(current_score) iterations += 1 next_state = None neighbors = current_state.get_neighbors() while ( next_state is None and neighbors ): # till we do not find a neighbor that we can move to index = random.randint(0, len(neighbors) - 1) # picking a random neighbor picked_neighbor = neighbors.pop(index) change = picked_neighbor.score() - current_score if ( picked_neighbor.x > max_x or picked_neighbor.x < min_x or picked_neighbor.y > max_y or picked_neighbor.y < min_y ): continue # neighbor outside our bounds if not find_max: change = change * -1 # in case we are finding minimum if change > 0: # improves the solution next_state = picked_neighbor else: probability = (math.e) ** ( change / current_temp ) # probability generation function if random.random() < probability: # random number within probability next_state = picked_neighbor current_temp = current_temp - (current_temp * rate_of_decrease) if current_temp < threshold_temp or next_state is None: # temperature below threshold, or could not find a suitable neighbor search_end = True else: current_state = next_state if visualization: from matplotlib import pyplot as plt plt.plot(range(iterations), scores) plt.xlabel("Iterations") plt.ylabel("Function values") plt.show() return best_state
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def test_f1(x, y): return (x**2) + (y**2)
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def test_f2(x, y): return (3 * x**2) - (6 * y)
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def __init__(self, x: int, y: int, step_size: int, function_to_optimize): self.x = x self.y = y self.step_size = step_size self.function = function_to_optimize
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def score(self) -> int: return self.function(self.x, self.y)
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def get_neighbors(self): step_size = self.step_size return [ SearchProblem(x, y, step_size, self.function) for x, y in ( (self.x - step_size, self.y - step_size), (self.x - step_size, self.y), (self.x - step_size, self.y + step_size), (self.x, self.y - step_size), (self.x, self.y + step_size), (self.x + step_size, self.y - step_size), (self.x + step_size, self.y), (self.x + step_size, self.y + step_size), ) ]
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def __hash__(self): return hash(str(self))
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def __eq__(self, obj): if isinstance(obj, SearchProblem): return hash(str(self)) == hash(str(obj)) return False
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def __str__(self): return f"x: {self.x} y: {self.y}"
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def hill_climbing( search_prob, find_max: bool = True, max_x: float = math.inf, min_x: float = -math.inf, max_y: float = math.inf, min_y: float = -math.inf, visualization: bool = False, max_iter: int = 10000, ) -> SearchProblem: current_state = search_prob scores = [] # list to store the current score at each iteration iterations = 0 solution_found = False visited = set() while not solution_found and iterations < max_iter: visited.add(current_state) iterations += 1 current_score = current_state.score() scores.append(current_score) neighbors = current_state.get_neighbors() max_change = -math.inf min_change = math.inf next_state = None # to hold the next best neighbor for neighbor in neighbors: if neighbor in visited: continue # do not want to visit the same state again if ( neighbor.x > max_x or neighbor.x < min_x or neighbor.y > max_y or neighbor.y < min_y ): continue # neighbor outside our bounds change = neighbor.score() - current_score if find_max: # finding max # going to direction with greatest ascent if change > max_change and change > 0: max_change = change next_state = neighbor else: # finding min # to direction with greatest descent if change < min_change and change < 0: min_change = change next_state = neighbor if next_state is not None: # we found at least one neighbor which improved the current state current_state = next_state else: # since we have no neighbor that improves the solution we stop the search solution_found = True if visualization: from matplotlib import pyplot as plt plt.plot(range(iterations), scores) plt.xlabel("Iterations") plt.ylabel("Function values") plt.show() return current_state
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def test_f1(x, y): return (x**2) + (y**2)
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def test_f2(x, y): return (3 * x**2) - (6 * y)
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def bisect_left( sorted_collection: list[int], item: int, lo: int = 0, hi: int = -1 ) -> int: if hi < 0: hi = len(sorted_collection) while lo < hi: mid = lo + (hi - lo) // 2 if sorted_collection[mid] < item: lo = mid + 1 else: hi = mid return lo
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def bisect_right( sorted_collection: list[int], item: int, lo: int = 0, hi: int = -1 ) -> int: if hi < 0: hi = len(sorted_collection) while lo < hi: mid = lo + (hi - lo) // 2 if sorted_collection[mid] <= item: lo = mid + 1 else: hi = mid return lo
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def insort_left( sorted_collection: list[int], item: int, lo: int = 0, hi: int = -1 ) -> None: sorted_collection.insert(bisect_left(sorted_collection, item, lo, hi), item)
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def insort_right( sorted_collection: list[int], item: int, lo: int = 0, hi: int = -1 ) -> None: sorted_collection.insert(bisect_right(sorted_collection, item, lo, hi), item)
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def binary_search(sorted_collection: list[int], item: int) -> int | None: left = 0 right = len(sorted_collection) - 1 while left <= right: midpoint = left + (right - left) // 2 current_item = sorted_collection[midpoint] if current_item == item: return midpoint elif item < current_item: right = midpoint - 1 else: left = midpoint + 1 return None
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def binary_search_std_lib(sorted_collection: list[int], item: int) -> int | None: index = bisect.bisect_left(sorted_collection, item) if index != len(sorted_collection) and sorted_collection[index] == item: return index return None
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def binary_search_by_recursion( sorted_collection: list[int], item: int, left: int, right: int ) -> int | None: if right < left: return None midpoint = left + (right - left) // 2 if sorted_collection[midpoint] == item: return midpoint elif sorted_collection[midpoint] > item: return binary_search_by_recursion(sorted_collection, item, left, midpoint - 1) else: return binary_search_by_recursion(sorted_collection, item, midpoint + 1, right)
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def double_linear_search(array: list[int], search_item: int) -> int: # define the start and end index of the given array start_ind, end_ind = 0, len(array) - 1 while start_ind <= end_ind: if array[start_ind] == search_item: return start_ind elif array[end_ind] == search_item: return end_ind else: start_ind += 1 end_ind -= 1 # returns -1 if search_item is not found in array return -1
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def search(list_data: list, key: int, left: int = 0, right: int = 0) -> int: right = right or len(list_data) - 1 if left > right: return -1 elif list_data[left] == key: return left elif list_data[right] == key: return right else: return search(list_data, key, left + 1, right - 1)
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def sentinel_linear_search(sequence, target): sequence.append(target) index = 0 while sequence[index] != target: index += 1 sequence.pop() if index == len(sequence): return None return index
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def _partition(data: list, pivot) -> tuple: less, equal, greater = [], [], [] for element in data: if element < pivot: less.append(element) elif element > pivot: greater.append(element) else: equal.append(element) return less, equal, greater
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def lin_search(left: int, right: int, array: list[int], target: int) -> int: for i in range(left, right): if array[i] == target: return i return -1
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def ite_ternary_search(array: list[int], target: int) -> int: left = 0 right = len(array) while left <= right: if right - left < precision: return lin_search(left, right, array, target) one_third = (left + right) // 3 + 1 two_third = 2 * (left + right) // 3 + 1 if array[one_third] == target: return one_third elif array[two_third] == target: return two_third elif target < array[one_third]: right = one_third - 1 elif array[two_third] < target: left = two_third + 1 else: left = one_third + 1 right = two_third - 1 else: return -1
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def rec_ternary_search(left: int, right: int, array: list[int], target: int) -> int: if left < right: if right - left < precision: return lin_search(left, right, array, target) one_third = (left + right) // 3 + 1 two_third = 2 * (left + right) // 3 + 1 if array[one_third] == target: return one_third elif array[two_third] == target: return two_third elif target < array[one_third]: return rec_ternary_search(left, one_third - 1, array, target) elif array[two_third] < target: return rec_ternary_search(two_third + 1, right, array, target) else: return rec_ternary_search(one_third + 1, two_third - 1, array, target) else: return -1
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def __init__(self, data): self.data = data self.right = None self.left = None
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def build_tree(): print("\n********Press N to stop entering at any point of time********\n") check = input("Enter the value of the root node: ").strip().lower() or "n" if check == "n": return None q: queue.Queue = queue.Queue() tree_node = TreeNode(int(check)) q.put(tree_node) while not q.empty(): node_found = q.get() msg = f"Enter the left node of {node_found.data}: " check = input(msg).strip().lower() or "n" if check == "n": return tree_node left_node = TreeNode(int(check)) node_found.left = left_node q.put(left_node) msg = f"Enter the right node of {node_found.data}: " check = input(msg).strip().lower() or "n" if check == "n": return tree_node right_node = TreeNode(int(check)) node_found.right = right_node q.put(right_node) return None
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def pre_order(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return print(node.data, end=",") pre_order(node.left) pre_order(node.right)
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def in_order(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return in_order(node.left) print(node.data, end=",") in_order(node.right)
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def post_order(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return post_order(node.left) post_order(node.right) print(node.data, end=",")
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def level_order(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return q: queue.Queue = queue.Queue() q.put(node) while not q.empty(): node_dequeued = q.get() print(node_dequeued.data, end=",") if node_dequeued.left: q.put(node_dequeued.left) if node_dequeued.right: q.put(node_dequeued.right)
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def level_order_actual(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return q: queue.Queue = queue.Queue() q.put(node) while not q.empty(): list_ = [] while not q.empty(): node_dequeued = q.get() print(node_dequeued.data, end=",") if node_dequeued.left: list_.append(node_dequeued.left) if node_dequeued.right: list_.append(node_dequeued.right) print() for node in list_: q.put(node)
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def pre_order_iter(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return stack: list[TreeNode] = [] n = node while n or stack: while n: # start from root node, find its left child print(n.data, end=",") stack.append(n) n = n.left # end of while means current node doesn't have left child n = stack.pop() # start to traverse its right child n = n.right
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def in_order_iter(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return stack: list[TreeNode] = [] n = node while n or stack: while n: stack.append(n) n = n.left n = stack.pop() print(n.data, end=",") n = n.right
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def post_order_iter(node: TreeNode) -> None: if not isinstance(node, TreeNode) or not node: return stack1, stack2 = [], [] n = node stack1.append(n) while stack1: # to find the reversed order of post order, store it in stack2 n = stack1.pop() if n.left: stack1.append(n.left) if n.right: stack1.append(n.right) stack2.append(n) while stack2: # pop up from stack2 will be the post order print(stack2.pop().data, end=",")
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def prompt(s: str = "", width=50, char="*") -> str: if not s: return "\n" + width * char left, extra = divmod(width - len(s) - 2, 2) return f"{left * char} {s} {(left + extra) * char}"
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def linear_search(sequence: list, target: int) -> int: for index, item in enumerate(sequence): if item == target: return index return -1
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def rec_linear_search(sequence: list, low: int, high: int, target: int) -> int: if not (0 <= high < len(sequence) and 0 <= low < len(sequence)): raise Exception("Invalid upper or lower bound!") if high < low: return -1 if sequence[low] == target: return low if sequence[high] == target: return high return rec_linear_search(sequence, low + 1, high - 1, target)
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def generate_neighbours(path): dict_of_neighbours = {} with open(path) as f: for line in f: if line.split()[0] not in dict_of_neighbours: _list = [] _list.append([line.split()[1], line.split()[2]]) dict_of_neighbours[line.split()[0]] = _list else: dict_of_neighbours[line.split()[0]].append( [line.split()[1], line.split()[2]] ) if line.split()[1] not in dict_of_neighbours: _list = [] _list.append([line.split()[0], line.split()[2]]) dict_of_neighbours[line.split()[1]] = _list else: dict_of_neighbours[line.split()[1]].append( [line.split()[0], line.split()[2]] ) return dict_of_neighbours
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def generate_first_solution(path, dict_of_neighbours): with open(path) as f: start_node = f.read(1) end_node = start_node first_solution = [] visiting = start_node distance_of_first_solution = 0 while visiting not in first_solution: minim = 10000 for k in dict_of_neighbours[visiting]: if int(k[1]) < int(minim) and k[0] not in first_solution: minim = k[1] best_node = k[0] first_solution.append(visiting) distance_of_first_solution = distance_of_first_solution + int(minim) visiting = best_node first_solution.append(end_node) position = 0 for k in dict_of_neighbours[first_solution[-2]]: if k[0] == start_node: break position += 1 distance_of_first_solution = ( distance_of_first_solution + int(dict_of_neighbours[first_solution[-2]][position][1]) - 10000 ) return first_solution, distance_of_first_solution
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def find_neighborhood(solution, dict_of_neighbours): neighborhood_of_solution = [] for n in solution[1:-1]: idx1 = solution.index(n) for kn in solution[1:-1]: idx2 = solution.index(kn) if n == kn: continue _tmp = copy.deepcopy(solution) _tmp[idx1] = kn _tmp[idx2] = n distance = 0 for k in _tmp[:-1]: next_node = _tmp[_tmp.index(k) + 1] for i in dict_of_neighbours[k]: if i[0] == next_node: distance = distance + int(i[1]) _tmp.append(distance) if _tmp not in neighborhood_of_solution: neighborhood_of_solution.append(_tmp) index_of_last_item_in_the_list = len(neighborhood_of_solution[0]) - 1 neighborhood_of_solution.sort(key=lambda x: x[index_of_last_item_in_the_list]) return neighborhood_of_solution
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def tabu_search( first_solution, distance_of_first_solution, dict_of_neighbours, iters, size ): count = 1 solution = first_solution tabu_list = [] best_cost = distance_of_first_solution best_solution_ever = solution while count <= iters: neighborhood = find_neighborhood(solution, dict_of_neighbours) index_of_best_solution = 0 best_solution = neighborhood[index_of_best_solution] best_cost_index = len(best_solution) - 1 found = False while not found: i = 0 while i < len(best_solution): if best_solution[i] != solution[i]: first_exchange_node = best_solution[i] second_exchange_node = solution[i] break i = i + 1 if [first_exchange_node, second_exchange_node] not in tabu_list and [ second_exchange_node, first_exchange_node, ] not in tabu_list: tabu_list.append([first_exchange_node, second_exchange_node]) found = True solution = best_solution[:-1] cost = neighborhood[index_of_best_solution][best_cost_index] if cost < best_cost: best_cost = cost best_solution_ever = solution else: index_of_best_solution = index_of_best_solution + 1 best_solution = neighborhood[index_of_best_solution] if len(tabu_list) >= size: tabu_list.pop(0) count = count + 1 return best_solution_ever, best_cost
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def main(args=None): dict_of_neighbours = generate_neighbours(args.File) first_solution, distance_of_first_solution = generate_first_solution( args.File, dict_of_neighbours ) best_sol, best_cost = tabu_search( first_solution, distance_of_first_solution, dict_of_neighbours, args.Iterations, args.Size, ) print(f"Best solution: {best_sol}, with total distance: {best_cost}.")
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def interpolation_search(sorted_collection, item): left = 0 right = len(sorted_collection) - 1 while left <= right: # avoid divided by 0 during interpolation if sorted_collection[left] == sorted_collection[right]: if sorted_collection[left] == item: return left else: return None point = left + ((item - sorted_collection[left]) * (right - left)) // ( sorted_collection[right] - sorted_collection[left] ) # out of range check if point < 0 or point >= len(sorted_collection): return None current_item = sorted_collection[point] if current_item == item: return point else: if point < left: right = left left = point elif point > right: left = right right = point else: if item < current_item: right = point - 1 else: left = point + 1 return None
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def interpolation_search_by_recursion(sorted_collection, item, left, right): # avoid divided by 0 during interpolation if sorted_collection[left] == sorted_collection[right]: if sorted_collection[left] == item: return left else: return None point = left + ((item - sorted_collection[left]) * (right - left)) // ( sorted_collection[right] - sorted_collection[left] ) # out of range check if point < 0 or point >= len(sorted_collection): return None if sorted_collection[point] == item: return point elif point < left: return interpolation_search_by_recursion(sorted_collection, item, point, left) elif point > right: return interpolation_search_by_recursion(sorted_collection, item, right, left) else: if sorted_collection[point] > item: return interpolation_search_by_recursion( sorted_collection, item, left, point - 1 ) else: return interpolation_search_by_recursion( sorted_collection, item, point + 1, right )
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def __assert_sorted(collection): if collection != sorted(collection): raise ValueError("Collection must be ascending sorted") return True
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def fibonacci(k: int) -> int: if not isinstance(k, int): raise TypeError("k must be an integer.") if k < 0: raise ValueError("k integer must be greater or equal to zero.") if k == 0: return 0 elif k == 1: return 1 else: return fibonacci(k - 1) + fibonacci(k - 2)
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def fibonacci_search(arr: list, val: int) -> int: len_list = len(arr) # Find m such that F_m >= n where F_i is the i_th fibonacci number. i = 0 while True: if fibonacci(i) >= len_list: fibb_k = i break i += 1 offset = 0 while fibb_k > 0: index_k = min( offset + fibonacci(fibb_k - 1), len_list - 1 ) # Prevent out of range item_k_1 = arr[index_k] if item_k_1 == val: return index_k elif val < item_k_1: fibb_k -= 1 elif val > item_k_1: offset += fibonacci(fibb_k - 1) fibb_k -= 2 else: return -1
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def jump_search(arr: list, x: int) -> int: n = len(arr) step = int(math.floor(math.sqrt(n))) prev = 0 while arr[min(step, n) - 1] < x: prev = step step += int(math.floor(math.sqrt(n))) if prev >= n: return -1 while arr[prev] < x: prev = prev + 1 if prev == min(step, n): return -1 if arr[prev] == x: return prev return -1
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def __init__(self, data: int) -> None: self.data = data self.rank: int self.parent: Node
data_structures
def make_set(x: Node) -> None: # rank is the distance from x to its' parent # root's rank is 0 x.rank = 0 x.parent = x
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def union_set(x: Node, y: Node) -> None: x, y = find_set(x), find_set(y) if x == y: return elif x.rank > y.rank: y.parent = x else: x.parent = y if x.rank == y.rank: y.rank += 1
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def find_set(x: Node) -> Node: if x != x.parent: x.parent = find_set(x.parent) return x.parent
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def find_python_set(node: Node) -> set: sets = ({0, 1, 2}, {3, 4, 5}) for s in sets: if node.data in s: return s raise ValueError(f"{node.data} is not in {sets}")
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def test_disjoint_set() -> None: vertex = [Node(i) for i in range(6)] for v in vertex: make_set(v) union_set(vertex[0], vertex[1]) union_set(vertex[1], vertex[2]) union_set(vertex[3], vertex[4]) union_set(vertex[3], vertex[5]) for node0 in vertex: for node1 in vertex: if find_python_set(node0).isdisjoint(find_python_set(node1)): assert find_set(node0) != find_set(node1) else: assert find_set(node0) == find_set(node1)
data_structures
def __init__(self, set_counts: list) -> None: self.set_counts = set_counts self.max_set = max(set_counts) num_sets = len(set_counts) self.ranks = [1] * num_sets self.parents = list(range(num_sets))
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def merge(self, src: int, dst: int) -> bool: src_parent = self.get_parent(src) dst_parent = self.get_parent(dst) if src_parent == dst_parent: return False if self.ranks[dst_parent] >= self.ranks[src_parent]: self.set_counts[dst_parent] += self.set_counts[src_parent] self.set_counts[src_parent] = 0 self.parents[src_parent] = dst_parent if self.ranks[dst_parent] == self.ranks[src_parent]: self.ranks[dst_parent] += 1 joined_set_size = self.set_counts[dst_parent] else: self.set_counts[src_parent] += self.set_counts[dst_parent] self.set_counts[dst_parent] = 0 self.parents[dst_parent] = src_parent joined_set_size = self.set_counts[src_parent] self.max_set = max(self.max_set, joined_set_size) return True
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def next_greatest_element_slow(arr: list[float]) -> list[float]: result = [] arr_size = len(arr) for i in range(arr_size): next_element: float = -1 for j in range(i + 1, arr_size): if arr[i] < arr[j]: next_element = arr[j] break result.append(next_element) return result
data_structures
def next_greatest_element_fast(arr: list[float]) -> list[float]: result = [] for i, outer in enumerate(arr): next_item: float = -1 for inner in arr[i + 1 :]: if outer < inner: next_item = inner break result.append(next_item) return result
data_structures
def next_greatest_element(arr: list[float]) -> list[float]: arr_size = len(arr) stack: list[float] = [] result: list[float] = [-1] * arr_size for index in reversed(range(arr_size)): if stack: while stack[-1] <= arr[index]: stack.pop() if not stack: break if stack: result[index] = stack[-1] stack.append(arr[index]) return result
data_structures
def is_operand(c): return c.isdigit()
data_structures
def evaluate(expression): stack = [] # iterate over the string in reverse order for c in expression.split()[::-1]: # push operand to stack if is_operand(c): stack.append(int(c)) else: # pop values from stack can calculate the result # push the result onto the stack again o1 = stack.pop() o2 = stack.pop() stack.append(calc[c](o1, o2)) return stack.pop()
data_structures
def dijkstras_two_stack_algorithm(equation: str) -> int: operators = {"*": op.mul, "/": op.truediv, "+": op.add, "-": op.sub} operand_stack: Stack[int] = Stack() operator_stack: Stack[str] = Stack() for i in equation: if i.isdigit(): # RULE 1 operand_stack.push(int(i)) elif i in operators: # RULE 2 operator_stack.push(i) elif i == ")": # RULE 4 opr = operator_stack.peek() operator_stack.pop() num1 = operand_stack.peek() operand_stack.pop() num2 = operand_stack.peek() operand_stack.pop() total = operators[opr](num2, num1) operand_stack.push(total) # RULE 5 return operand_stack.peek()
data_structures
def infix_2_postfix(infix): stack = [] post_fix = [] priority = { "^": 3, "*": 2, "/": 2, "%": 2, "+": 1, "-": 1, } # Priority of each operator print_width = len(infix) if (len(infix) > 7) else 7 # Print table header for output print( "Symbol".center(8), "Stack".center(print_width), "Postfix".center(print_width), sep=" | ", ) print("-" * (print_width * 3 + 7)) for x in infix: if x.isalpha() or x.isdigit(): post_fix.append(x) # if x is Alphabet / Digit, add it to Postfix elif x == "(": stack.append(x) # if x is "(" push to Stack elif x == ")": # if x is ")" pop stack until "(" is encountered while stack[-1] != "(": post_fix.append(stack.pop()) # Pop stack & add the content to Postfix stack.pop() else: if len(stack) == 0: stack.append(x) # If stack is empty, push x to stack else: # while priority of x is not > priority of element in the stack while len(stack) > 0 and priority[x] <= priority[stack[-1]]: post_fix.append(stack.pop()) # pop stack & add to Postfix stack.append(x) # push x to stack print( x.center(8), ("".join(stack)).ljust(print_width), ("".join(post_fix)).ljust(print_width), sep=" | ", ) # Output in tabular format while len(stack) > 0: # while stack is not empty post_fix.append(stack.pop()) # pop stack & add to Postfix print( " ".center(8), ("".join(stack)).ljust(print_width), ("".join(post_fix)).ljust(print_width), sep=" | ", ) # Output in tabular format return "".join(post_fix) # return Postfix as str
data_structures
def infix_2_prefix(infix): infix = list(infix[::-1]) # reverse the infix equation for i in range(len(infix)): if infix[i] == "(": infix[i] = ")" # change "(" to ")" elif infix[i] == ")": infix[i] = "(" # change ")" to "(" return (infix_2_postfix("".join(infix)))[ ::-1 ] # call infix_2_postfix on Infix, return reverse of Postfix
data_structures
def __init__(self, data: T): self.data = data # Assign data self.next: Node[T] | None = None # Initialize next as null self.prev: Node[T] | None = None # Initialize prev as null
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def __init__(self) -> None: self.head: Node[T] | None = None
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def push(self, data: T) -> None: if self.head is None: return None else: assert self.head is not None temp = self.head.data self.head = self.head.next if self.head is not None: self.head.prev = None return temp
data_structures
def balanced_parentheses(parentheses: str) -> bool: stack: Stack[str] = Stack() bracket_pairs = {"(": ")", "[": "]", "{": "}"} for bracket in parentheses: if bracket in bracket_pairs: stack.push(bracket) elif bracket in (")", "]", "}"): if stack.is_empty() or bracket_pairs[stack.pop()] != bracket: return False return stack.is_empty()
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def evaluate_postfix(postfix_notation: list) -> int: if not postfix_notation: return 0 operations = {"+", "-", "*", "/"} stack: list[Any] = [] for token in postfix_notation: if token in operations: b, a = stack.pop(), stack.pop() if token == "+": stack.append(a + b) elif token == "-": stack.append(a - b) elif token == "*": stack.append(a * b) else: if a * b < 0 and a % b != 0: stack.append(a // b + 1) else: stack.append(a // b) else: stack.append(int(token)) return stack.pop()
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def calculation_span(price, s): n = len(price) # Create a stack and push index of fist element to it st = [] st.append(0) # Span value of first element is always 1 s[0] = 1 # Calculate span values for rest of the elements for i in range(1, n): # Pop elements from stack while stack is not # empty and top of stack is smaller than price[i] while len(st) > 0 and price[st[0]] <= price[i]: st.pop() # If stack becomes empty, then price[i] is greater # than all elements on left of it, i.e. price[0], # price[1], ..price[i-1]. Else the price[i] is # greater than elements after top of stack s[i] = i + 1 if len(st) <= 0 else (i - st[0]) # Push this element to stack st.append(i)
data_structures
def print_array(arr, n): for i in range(0, n): print(arr[i], end=" ")
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def __init__(self, limit: int = 10): self.stack: list[T] = [] self.limit = limit
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def __bool__(self) -> bool: return bool(self.stack)
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def __str__(self) -> str: return str(self.stack)
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def push(self, data: T) -> None: Pop an element off of the top of the stack. >>> Stack().pop() Traceback (most recent call last): ... data_structures.stacks.stack.StackUnderflowError Peek at the top-most element of the stack. >>> Stack().pop() Traceback (most recent call last): ... data_structures.stacks.stack.StackUnderflowError return not bool(self.stack)
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def is_full(self) -> bool: return self.size() == self.limit
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def size(self) -> int: return item in self.stack
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def test_stack() -> None: stack: Stack[int] = Stack(10) assert bool(stack) is False assert stack.is_empty() is True assert stack.is_full() is False assert str(stack) == "[]" try: _ = stack.pop() raise AssertionError() # This should not happen except StackUnderflowError: assert True # This should happen try: _ = stack.peek() raise AssertionError() # This should not happen except StackUnderflowError: assert True # This should happen for i in range(10): assert stack.size() == i stack.push(i) assert bool(stack) assert not stack.is_empty() assert stack.is_full() assert str(stack) == str(list(range(10))) assert stack.pop() == 9 assert stack.peek() == 8 stack.push(100) assert str(stack) == str([0, 1, 2, 3, 4, 5, 6, 7, 8, 100]) try: stack.push(200) raise AssertionError() # This should not happen except StackOverflowError: assert True # This should happen assert not stack.is_empty() assert stack.size() == 10 assert 5 in stack assert 55 not in stack
data_structures
def precedence(char: str) -> int: return {"+": 1, "-": 1, "*": 2, "/": 2, "^": 3}.get(char, -1)
data_structures
def infix_to_postfix(expression_str: str) -> str: if not balanced_parentheses(expression_str): raise ValueError("Mismatched parentheses") stack: Stack[str] = Stack() postfix = [] for char in expression_str: if char.isalpha() or char.isdigit(): postfix.append(char) elif char == "(": stack.push(char) elif char == ")": while not stack.is_empty() and stack.peek() != "(": postfix.append(stack.pop()) stack.pop() else: while not stack.is_empty() and precedence(char) <= precedence(stack.peek()): postfix.append(stack.pop()) stack.push(char) while not stack.is_empty(): postfix.append(stack.pop()) return " ".join(postfix)
data_structures
def solve(post_fix): stack = [] div = lambda x, y: int(x / y) # noqa: E731 integer division operation opr = { "^": op.pow, "*": op.mul, "/": div, "+": op.add, "-": op.sub, } # operators & their respective operation # print table header print("Symbol".center(8), "Action".center(12), "Stack", sep=" | ") print("-" * (30 + len(post_fix))) for x in post_fix: if x.isdigit(): # if x in digit stack.append(x) # append x to stack # output in tabular format print(x.rjust(8), ("push(" + x + ")").ljust(12), ",".join(stack), sep=" | ") else: b = stack.pop() # pop stack # output in tabular format print("".rjust(8), ("pop(" + b + ")").ljust(12), ",".join(stack), sep=" | ") a = stack.pop() # pop stack # output in tabular format print("".rjust(8), ("pop(" + a + ")").ljust(12), ",".join(stack), sep=" | ") stack.append( str(opr[x](int(a), int(b))) ) # evaluate the 2 values popped from stack & push result to stack # output in tabular format print( x.rjust(8), ("push(" + a + x + b + ")").ljust(12), ",".join(stack), sep=" | ", ) return int(stack[0])
data_structures
def binary_tree_mirror_dict(binary_tree_mirror_dictionary: dict, root: int): if not root or root not in binary_tree_mirror_dictionary: return left_child, right_child = binary_tree_mirror_dictionary[root][:2] binary_tree_mirror_dictionary[root] = [right_child, left_child] binary_tree_mirror_dict(binary_tree_mirror_dictionary, left_child) binary_tree_mirror_dict(binary_tree_mirror_dictionary, right_child)
data_structures
def binary_tree_mirror(binary_tree: dict, root: int = 1) -> dict: if not binary_tree: raise ValueError("binary tree cannot be empty") if root not in binary_tree: raise ValueError(f"root {root} is not present in the binary_tree") binary_tree_mirror_dictionary = dict(binary_tree) binary_tree_mirror_dict(binary_tree_mirror_dictionary, root) return binary_tree_mirror_dictionary
data_structures
def __init__(self, length: int) -> None: self.minn: int = -1 self.maxx: int = -1 self.map_left: list[int] = [-1] * length self.left: Node | None = None self.right: Node | None = None
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def __repr__(self) -> str: return f"Node(min_value={self.minn} max_value={self.maxx})"
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def build_tree(arr: list[int]) -> Node | None: root = Node(len(arr)) root.minn, root.maxx = min(arr), max(arr) # Leaf node case where the node contains only one unique value if root.minn == root.maxx: return root pivot = (root.minn + root.maxx) // 2 left_arr: list[int] = [] right_arr: list[int] = [] for index, num in enumerate(arr): if num <= pivot: left_arr.append(num) else: right_arr.append(num) root.map_left[index] = len(left_arr) root.left = build_tree(left_arr) root.right = build_tree(right_arr) return root
data_structures
def rank_till_index(node: Node | None, num: int, index: int) -> int: if index < 0 or node is None: return 0 # Leaf node cases if node.minn == node.maxx: return index + 1 if node.minn == num else 0 pivot = (node.minn + node.maxx) // 2 if num <= pivot: # go the left subtree and map index to the left subtree return rank_till_index(node.left, num, node.map_left[index] - 1) else: # go to the right subtree and map index to the right subtree return rank_till_index(node.right, num, index - node.map_left[index])
data_structures
def rank(node: Node | None, num: int, start: int, end: int) -> int: if start > end: return 0 rank_till_end = rank_till_index(node, num, end) rank_before_start = rank_till_index(node, num, start - 1) return rank_till_end - rank_before_start
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def quantile(node: Node | None, index: int, start: int, end: int) -> int: if index > (end - start) or start > end or node is None: return -1 # Leaf node case if node.minn == node.maxx: return node.minn # Number of elements in the left subtree in interval [start, end] num_elements_in_left_tree = node.map_left[end] - ( node.map_left[start - 1] if start else 0 ) if num_elements_in_left_tree > index: return quantile( node.left, index, (node.map_left[start - 1] if start else 0), node.map_left[end] - 1, ) else: return quantile( node.right, index - num_elements_in_left_tree, start - (node.map_left[start - 1] if start else 0), end - node.map_left[end], )
data_structures
def range_counting( node: Node | None, start: int, end: int, start_num: int, end_num: int ) -> int: if ( start > end or node is None or start_num > end_num or node.minn > end_num or node.maxx < start_num ): return 0 if start_num <= node.minn and node.maxx <= end_num: return end - start + 1 left = range_counting( node.left, (node.map_left[start - 1] if start else 0), node.map_left[end] - 1, start_num, end_num, ) right = range_counting( node.right, start - (node.map_left[start - 1] if start else 0), end - node.map_left[end], start_num, end_num, ) return left + right
data_structures
def __init__(self, value: int = 0) -> None: self.value = value self.left: Node | None = None self.right: Node | None = None
data_structures
def merge_two_binary_trees(tree1: Node | None, tree2: Node | None) -> Node | None: if tree1 is None: return tree2 if tree2 is None: return tree1 tree1.value = tree1.value + tree2.value tree1.left = merge_two_binary_trees(tree1.left, tree2.left) tree1.right = merge_two_binary_trees(tree1.right, tree2.right) return tree1
data_structures
def print_preorder(root: Node | None) -> None: if root: print(root.value) print_preorder(root.left) print_preorder(root.right)
data_structures