Problem:
 Score : 600 points    Problem Statement We have N points numbered 1 to N arranged in a line in this order.  Takahashi decides to make an undirected graph, using these points as the vertices.
In the beginning, the graph has no edge. Takahashi will do M operations to add edges in this graph.
The i -th operation is as follows:   The operation uses integers L_i and R_i between 1 and N (inclusive), and a positive integer C_i . For every pair of integers (s, t) such that L_i \leq s < t \leq R_i , add an edge of length C_i between Vertex s and Vertex t .   The integers L_1, ..., L_M , R_1, ..., R_M , C_1, ..., C_M are all given as input.  Takahashi wants to solve the shortest path problem in the final graph obtained. Find the length of the shortest path from Vertex 1 to Vertex N in the final graph.      Constraints  2 \leq N \leq 10^5  1 \leq M \leq 10^5  1 \leq L_i < R_i \leq N  1 \leq C_i \leq 10^9         Input Input is given from Standard Input in the following format:  N  M  L_1  R_1  C_1  :  L_M  R_M  C_M       Output Print the length of the shortest path from Vertex 1 to Vertex N in the final graph.
If there is no shortest path, print -1 instead.        Sample Input 1 4 3
1 3 2
2 4 3
1 4 6      Sample Output 1 5  We have an edge of length 2 between Vertex 1 and Vertex 2 , and an edge of length 3 between Vertex 2 and Vertex 4 , so there is a path of length 5 between Vertex 1 and Vertex 4 .       Sample Input 2 4 2
1 2 1
3 4 2      Sample Output 2 -1       Sample Input 3 10 7
1 5 18
3 4 8
1 3 5
4 7 10
5 9 8
6 10 5
8 10 3      Sample Output 3 28

Solution (Python):
import sys
import heapq
input = sys.stdin.readline


def dijkstra(s, E):
    inf = float('inf')
    d = [inf for i in range(len(E))]
    d[s] = 0
    q = [(0, s)]
    while q:
        c, p = heapq.heappop(q)
        if d[p] < c:
            continue
        for cost, to in E[p]:
            if d[to] > d[p] + cost:
                d[to] = d[p] + cost
                heapq.heappush(q, (d[to], to))
    return d


def main():
    N, M = map(int, input().split())
    E = [[] for _ in range(N)]
    for _ in range(M):
        s, t, c = map(int, input().split())
        E[s-1].append((c, t-1))
    for i in range(N-1):
        E[i+1].append((0, i))

    A = dijkstra(0, E)

    ans = A[N-1]
    if ans == float("inf"):
        print(-1)
    else:
        print(ans)


if __name__ == '__main__':
    main()

Solution (Python):
import sys
input = sys.stdin.readline
INF = 1 << 50


class SegTree():
    def __init__(self, n_, ele_id, operation_func):
        self.n = 1
        while self.n < n_:
            self.n *= 2
        self.data = [ele_id] * (2 * self.n - 1)
        self.ele_id = ele_id
        self.operation_func = operation_func

    def __getitem__(self, idx):
        return self.data[idx + self.n - 1]

    def update_all(self, data_init):
        for i in range(len(data_init)):
            self.data[i + self.n - 1] = data_init[i]
        for i in range(self.n - 2, -1, -1):
            self.data[i] = self.operation_func(self.data[2 * i + 1],
                                               self.data[2 * i + 2])

    def update(self, idx, x):
        
        idx += self.n - 1
        self.data[idx] = x
        while idx > 0:
            idx = (idx - 1) // 2
            self.data[idx] = self.operation_func(self.data[2 * idx + 1],
                                                 self.data[2 * idx + 2])

    def query(self, a, b):
        return self.query_(a, b, 0, 0, self.n)

    def query_(self, a, b, k, l, r):
        
        if r <= a or b <= l:
            
            return self.ele_id

        if a <= l and r <= b:
            
            return self.data[k]
        else:
            
            child_l = self.query_(a, b, 2 * k + 1, l, (l + r) // 2)
            child_r = self.query_(a, b, 2 * k + 2, (l + r) // 2, r)
            return self.operation_func(child_l, child_r)


n, m = map(int, input().split())
l_dict = [[] for _ in range(n)]
r_dict = [[] for _ in range(n)]
edge = []
for i in range(m):
    l, r, c = map(int, input().split())
    l -= 1
    r -= 1
    l_dict[l].append(i)
    r_dict[r].append(i)
    edge.append((l, r, c))

dp = [INF] * n
dp[0] = 0
seg_rmq = SegTree(n, INF, min)
seg_rmq.update(0, 0)

for i in range(1, n):
    for j in r_dict[i]:
        l, r, c = edge[j]
        tmp = seg_rmq.query(l, r)
        dp[i] = min(dp[i], tmp + c)

    seg_rmq.update(i, dp[i])

ans = dp[-1] if dp[-1] != INF else -1

print(ans)

Solution (Python):
class Rmq:
    
    
    def __init__(self, a, sqrt_n=500):
        from itertools import zip_longest
        self.n = len(a)
        self.sqrt_n = sqrt_n
        self.layer1 = a
        self.layer0 = [min(values) for values in zip_longest(*[iter(a)]*sqrt_n, fillvalue=float("inf"))]

    def get_min(self, l, r):
        sqrt_n = self.sqrt_n
        parent_l, parent_r = l//sqrt_n+1, (r+1)//sqrt_n
        if parent_l < parent_r:
            return min(min(self.layer0[parent_l:parent_r]),
                       min(self.layer1[l:parent_l*sqrt_n]),
                       min(self.layer1[parent_r*sqrt_n:r]))
        else:
            return min(self.layer1[l:r])

    def set_value(self, idx, val):
        self.layer1[idx] = val
        idx //= self.sqrt_n
        self.layer0[idx] = min(self.layer0[idx], val)

    def chmin(self, idx, val):
        if self.layer1[idx] > val:
            self.set_value(idx, val)

    def debug(self):
        print("layer0=", self.layer0)
        print("layer1=", self.layer1)

    def __getitem__(self, item):
        return self.layer1[item]

    def __setitem__(self, key, value):
        self.set_value(key, value)


from operator import itemgetter
import sys

def main():
    N, M = map(int, input().split())
    LRC = list(zip(*[iter(map(int, sys.stdin.read().split()))]*3))
    LRC.sort(key=itemgetter(0))
    idx_LRC = 0
    inf = 1 << 60

    rmq = Rmq([inf] * (N+1))
    rmq.set_value(1, 0)
    for v in range(1, N+1):
        d = rmq.get_min(v, N+1)
        while idx_LRC < M:
            l, r, c = LRC[idx_LRC]
            if l <= v:
                rmq.chmin(r, d+c)
                idx_LRC += 1
            else:
                break
    ans = rmq[N]
    print(ans if ans < inf else -1)

main()

Solution (Python):



class Rmq:
    
    
    def __init__(self, a, sqrt_n=500):
        from itertools import zip_longest
        self.n = len(a)
        self.sqrt_n = sqrt_n
        self.layer1 = a
        self.layer0 = [min(values) for values in zip_longest(*[iter(a)]*sqrt_n, fillvalue=float("inf"))]

    def get_min(self, l, r):
        sqrt_n = self.sqrt_n
        parent_l, parent_r = l//sqrt_n+1, (r+1)//sqrt_n
        if parent_l < parent_r:
            return min(min(self.layer0[parent_l:parent_r]),
                       min(self.layer1[l:parent_l*sqrt_n]),
                       min(self.layer1[parent_r*sqrt_n:r]))
        else:
            return min(self.layer1[l:r])

    def set_value(self, idx, val):
        self.layer1[idx] = val
        idx //= self.sqrt_n
        self.layer0[idx] = min(self.layer0[idx], val)

    def chmin(self, idx, val):
        if self.layer1[idx] > val:
            self.set_value(idx, val)

    def debug(self):
        print("layer0=", self.layer0)
        print("layer1=", self.layer1)

    def __getitem__(self, item):
        return self.layer1[item]

    def __setitem__(self, key, value):
        self.set_value(key, value)


from operator import itemgetter

N, M = map(int, input().split())
LRC = [list(map(int, input().split())) for _ in range(M)]
LRC.sort(key=itemgetter(0))

idx_LRC = 0
q = []

rmq = Rmq([float("inf")] * (N+1))

rmq.set_value(1, 0)
for v in range(1, N+1):
    d = rmq.get_min(v, N+1)
    while idx_LRC < M:
        l, r, c = LRC[idx_LRC]
        if l <= v:
            rmq.chmin(r, d+c)
            idx_LRC += 1
        else:
            break
ans = rmq[N]
print(ans if ans != float("inf") else -1)

Solution (Python):

import sys
from collections import defaultdict
from heapq import heappop, heappush


class Graph(object):

    def __init__(self):
        self.graph = defaultdict(list)

    def __len__(self):
        return len(self.graph)

    def add_edge(self, src, dst, weight=1):
        self.graph[src].append((dst, weight))

    def get_nodes(self):
        return self.graph.keys()


class Dijkstra(object):

    def __init__(self, graph, start):
        self.g = graph.graph

        self.dist = defaultdict(lambda: float('inf'))
        self.dist[start] = 0

        
        self.prev = defaultdict(lambda: None)

        
        self.Q = []
        heappush(self.Q, (self.dist[start], start))

        while self.Q:
            
            dist_u, u = heappop(self.Q)
            if self.dist[u] < dist_u:
                continue
            for v, weight in self.g[u]:
                alt = dist_u + weight
                if self.dist[v] > alt:
                    self.dist[v] = alt
                    self.prev[v] = u
                    heappush(self.Q, (alt, v))

    def shortest_distance(self, goal):
        return self.dist[goal]

    def shortest_path(self, goal):
        path = []
        node = goal
        while node is not None:
            path.append(node)
            node = self.prev[node]
        return path[::-1]

def solve(N: int, M: int, L: "List[int]", R: "List[int]", C: "List[int]"):
    graph= Graph()
    for i in range(M):
        graph.add_edge(L[i]-1,R[i]-1,C[i])
    for i in range(N-1):
        graph.add_edge(i+1,i,0)
    d = Dijkstra(graph,0)
    shortest = d.shortest_distance(N-1)
    
    if shortest == float('inf'):
        print(-1)
    else:
        print(shortest)
    return


def main():
    def iterate_tokens():
        for line in sys.stdin:
            for word in line.split():
                yield word
    tokens = iterate_tokens()
    N = int(next(tokens))  
    M = int(next(tokens))  
    L = [int()] * (M)  
    R = [int()] * (M)  
    C = [int()] * (M)  
    for i in range(M):
        L[i] = int(next(tokens))
        R[i] = int(next(tokens))
        C[i] = int(next(tokens))
    solve(N, M, L, R, C)

if __name__ == '__main__':
    main()

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [self.default_value] * (2 * self.size)

    def build(self):
        
        for i, x in enumerate([self.default_value] * (self.Nelem + 1)):
            self.data[self.size + i] = x
        for i in range(self.size - 1, 0, -1):
            x = self.data[i + i];
            y = self.data[i + i + 1]
            self.data[i] = x if x < y else y

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                x = min(x, y)
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                x = min(x, y)
            left >>= 1
            right >>= 1
        return x


def solve():
    readline = sys.stdin.buffer.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, readline().split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    stree.build()
    lrc = [list(map(int, readline().split())) for _ in range(m)]
    lrc.sort()
    stree.update(0, 0)
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r)
        now = stree.get_value(r, r)
        tm = tm + c if tm + c < now else now
        stree.update(r, tm)
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [default_value] * (2 * self.size)

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                x = min(x, y)
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                x = min(x, y)
            left >>= 1
            right >>= 1
        return x


def solve():
    readline = sys.stdin.buffer.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, readline().split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    lrc = [list(map(int, readline().split())) for _ in range(m)]
    lrc.sort()
    stree.update(0, 0)
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r)
        now = stree.get_value(r, r)
        tm = tm + c if tm + c < now else now
        stree.update(r, tm)
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):
import heapq
N,M = map(int,input().split())
LRC = [tuple(map(int,input().split())) for i in range(M)]

es = [[] for i in range(N)]
for l,r,c in LRC:
    l,r = l-1,r-1
    es[l].append((r,c))
for i in range(N-1):
    es[i+1].append((i,0))

INF = float('inf')
dist = [INF]*N
dist[0] = 0
hq = [(0,0)]
heapq.heapify(hq)

while(hq):
    d,v = heapq.heappop(hq)
    if v==N-1:
        print(d)
        exit()
    for to,c in es[v]:
        if d+c >= dist[to]: continue
        dist[to] = d+c
        heapq.heappush(hq, (d+c, to))
print(-1)

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [default_value] * (2 * self.size)

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                x = min(x, y)
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                x = min(x, y)
            left >>= 1
            right >>= 1
        return x


def solve():
    input = sys.stdin.buffer.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, input().split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    lrc = [list(map(int, input().split())) for _ in range(m)]
    lrc.sort()
    stree.update(0, 0)
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r)
        now = stree.get_value(r, r)
        tm = tm + c if tm + c < now else now
        stree.update(r, tm)
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):


import sys
def input(): return sys.stdin.readline().strip()
def list2d(a, b, c): return [[c] * b for i in range(a)]
def list3d(a, b, c, d): return [[[d] * c for k in range(b)] for i in range(a)]
def list4d(a, b, c, d, e): return [[[[e] * d for k in range(c)] for k in range(b)] for i in range(a)]
def ceil(x, y=1): return int(-(-x // y))
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(N=None): return list(MAP()) if N is None else [INT() for i in range(N)]
def Yes(): print('Yes')
def No(): print('No')
def YES(): print('YES')
def NO(): print('NO')
sys.setrecursionlimit(10 ** 9)
INF = 10 ** 18
MOD = 998244353

class SegTree:
    """
    セグメント木
    1.update:  i番目の値をxに更新する
    2.query: 区間[l, r)の値を得る
    """

    def __init__(self, n, func, intv, A=[]):
        """
        :param n: 要素数(0-indexed)
        :param func: 値の操作に使う関数(min, max, add, gcdなど)
        :param intv: 要素の初期値(単位元)
        :param A: 初期化に使うリスト(オプション)
        """
        self.n = n
        self.func = func
        self.intv = intv
        
        n2 = 1
        while n2 < n:
            n2 <<= 1
        self.n2 = n2
        self.tree = [self.intv] * (n2 << 1)
        
        if A:
            
            for i in range(n):
                self.tree[n2+i] = A[i]
            
            for i in range(n2-1, -1, -1):
                self.tree[i] = self.func(self.tree[i*2], self.tree[i*2+1])

    def update(self, i, x):
        """
        i番目の値をxに更新
        :param i: index(0-indexed)
        :param x: update value
        """
        i += self.n2
        self.tree[i] = x
        while i > 0:
            i >>= 1
            self.tree[i] = self.func(self.tree[i*2], self.tree[i*2+1])

    def query(self, a, b):
        """
        [a, b)の値を得る
        :param a: index(0-indexed)
        :param b: index(0-indexed)
        """
        l = a + self.n2
        r = b + self.n2
        s = self.intv
        while l < r:
            if r & 1:
                r -= 1
                s = self.func(s, self.tree[r])
            if l & 1:
                s = self.func(s, self.tree[l])
                l += 1
            l >>= 1
            r >>= 1
        return s

    def get(self, i):
        """ 一点取得 """
        return self.tree[i+self.n2]

    def all(self):
        """ 全区間[0, n)の取得 """
        return self.tree[1]

N, M = MAP()
LRC = []
for i in range(M):
    l, r, c = MAP()
    l -= 1
    r -= 1
    LRC.append((l, r, c))

LRC.sort()
st = SegTree(N, min, INF)
st.update(0, 0)
for l, r, c in LRC:
    mn = st.query(l, r+1)
    st.update(r, min(st.get(r), mn+c))

ans = st.get(N-1)
if ans != INF:
    print(st.get(N-1))
else:
    print(-1)

Solution (Python):
from heapq import heappop, heappush
N, M = map(int, input().split())
route_list = [[] for _ in range(N)]
for i in range(M):
    L, R, C = map(int, input().split())
    route_list[L-1].append((R-1, C))
for i in range(N-1):
    route_list[i+1].append((i, 0))

distance = [float("inf")] * N
distance[0] = 0  
q = [(0, 0)]

while q:
    _, u = heappop(q)
    for des, cost in route_list[u]:
        if distance[des] > distance[u] + cost:
            distance[des] = distance[u] + cost
            heappush(q, (distance[des], des))

print(distance[-1] if distance[-1] != float("inf") else -1)

Solution (Python):
import sys
input=sys.stdin.readline
n,m=map(int,input().split())
edge=[[] for i in range(n)]
for i in range(m):
  x,y,z=map(int,input().split())
  edge[x-1].append([z,y-1])
  edge[y-1].append([z,x-1])
for i in range(1,n):
  edge[i].append([0,i-1])

import heapq
def dijkstra_heap(s):
  d=[float("inf")]*n
  used=[True]*n 
  d[s]=0
  used[s]=False
  edgelist=[]
  for e in edge[s]:
    heapq.heappush(edgelist,e)
  while len(edgelist):
    minedge=heapq.heappop(edgelist)
    if not used[minedge[1]]:
      continue
    v=minedge[1]
    d[v]=minedge[0]
    used[v]=False
    for e in edge[v]:
      if used[e[1]]:
        heapq.heappush(edgelist,[e[0]+d[v],e[1]])
  return d

x=dijkstra_heap(0)[n-1]
if x==float("inf"):
  print(-1)
else:
  print(x)

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [default_value] * (2 * self.size)

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                x = min(x, y)
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                x = min(x, y)
            left >>= 1
            right >>= 1
        return x



def solve():
    input = sys.stdin.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, input().rstrip('\n').split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    lrc = [list(map(int, input().rstrip('\n').split())) for _ in range(m)]
    lrc.sort()
    stree.update(0, 0)
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r-1)
        now = stree.get_value(r, r)
        tm = tm + c if tm + c < now else now
        stree.update(r, tm)
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [default_value] * (2 * self.size)

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = x if x < y else y
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                if x > y:
                    x = y
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                if x > y:
                    x = y
            left >>= 1
            right >>= 1
        return x


def solve():
    input = sys.stdin.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, input().rstrip('\n').split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    lrc = [list(map(int, input().rstrip('\n').split())) for _ in range(m)]
    lrc.sort()
    stree.update(0, 0)
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r-1)
        now = stree.get_value(r, r)
        tm = tm + c if tm + c < now else now
        stree.update(r, tm)
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):
from heapq import *


def Dijkstra(G: list, source=0):
	INF = float("inf")
	V = len(G)
	D = [INF] * V
	vis = [False] * V
	H = [(0, source)]
	while H:
		dist, cur = heappop(H)
		if vis[cur]:
			continue
		vis[cur] = True
		for nxt, cost in G[cur]:
			t = dist + cost
			if D[nxt] > t:
				D[nxt] = t
				heappush(H, (t, nxt))
	return D[-1] if D[-1]!=INF else -1


N, M, *L = map(int, open(0).read().split())
G = [[(i - 1, 0)] for i in range(N)]
G[0] = []
for l, r, c in zip(*[iter(L)] * 3):
	G[l - 1].append((r - 1, c))
print(Dijkstra(G))

Solution (Python):
import operator
import os
import sys

if os.getenv("LOCAL"):
    sys.stdin = open("_in.txt", "r")

sys.setrecursionlimit(10 ** 9)
INF = float("inf")
IINF = 10 ** 18
MOD = 10 ** 9 + 7




class SegmentTree:
    
    def __init__(self, size, fn=operator.add, default=None, initial_values=None):
        """
        :param int size:
        :param callable fn: 区間に適用する関数。引数を 2 つ取る。min, max, operator.xor など
        :param default:
        :param list initial_values:
        """
        default = default or 0

        
        n = 1
        while n < size:
            n *= 2
        self._size = n
        self._fn = fn

        self._tree = [default] * (self._size * 2 - 1)
        if initial_values:
            i = self._size - 1
            for v in initial_values:
                self._tree[i] = v
                i += 1
            i = self._size - 2
            while i >= 0:
                self._tree[i] = self._fn(self._tree[i * 2 + 1], self._tree[i * 2 + 2])
                i -= 1

    def set(self, i, value):
        """
        i 番目に value を設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self._tree[x] = value

        while x > 0:
            x = (x - 1) // 2
            self._tree[x] = self._fn(self._tree[x * 2 + 1], self._tree[x * 2 + 2])

    def add(self, i, value):
        """
        もとの i 番目と value に fn を適用したものを i 番目に設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self.set(i, self._fn(self._tree[x], value))

    def get(self, from_i, to_i=None, k=0, L=None, r=None):
        """
        [from_i, to_i) に fn を適用した結果を返す
        :param int from_i:
        :param int to_i:
        :param int k: self._tree[k] が、[L, r) に fn を適用した結果を持つ
        :param int L:
        :param int r:
        :return:
        """
        if to_i is None:
            return self._tree[self._size - 1 + from_i]
        L = 0 if L is None else L
        r = self._size if r is None else r

        if from_i <= L and r <= to_i:
            return self._tree[k]

        if to_i <= L or r <= from_i:
            return None

        ret_L = self.get(from_i, to_i, k * 2 + 1, L, (L + r) // 2)
        ret_r = self.get(from_i, to_i, k * 2 + 2, (L + r) // 2, r)
        if ret_L is None:
            return ret_r
        if ret_r is None:
            return ret_L
        return self._fn(ret_L, ret_r)

    def __len__(self):
        return self._size


N, M = list(map(int, sys.stdin.readline().split()))
LRC = [list(map(int, sys.stdin.readline().split())) for _ in range(M)]

LRC.sort()
LRC = [(l - 1, r - 1, c) for l, r, c in LRC]
i = 0


dp = SegmentTree(N, fn=min, initial_values=[INF] * N)
dp.set(0, 0)
for pos in range(N):
    d = dp.get(pos, N)
    while i < M and LRC[i][0] == pos:
        l, r, c = LRC[i]
        dp.add(r, d + c)
        i += 1
ans = dp.get(N - 1)
if ans == INF:
    print(-1)
else:
    print(ans)

Solution (Python):
import operator
import os
import sys

if os.getenv("LOCAL"):
    sys.stdin = open("_in.txt", "r")

sys.setrecursionlimit(10 ** 9)
INF = float("inf")
IINF = 10 ** 18
MOD = 10 ** 9 + 7




class SegmentTree:
    
    def __init__(self, size, fn=operator.add, default=None, initial_values=None):
        """
        :param int size:
        :param callable fn: 区間に適用する関数。引数を 2 つ取る。min, max, operator.xor など
        :param default:
        :param list initial_values:
        """
        default = default or 0

        
        n = 1
        while n < size:
            n *= 2
        self._size = n
        self._fn = fn

        self._tree = [default] * (self._size * 2 - 1)
        if initial_values:
            i = self._size - 1
            for v in initial_values:
                self._tree[i] = v
                i += 1
            i = self._size - 2
            while i >= 0:
                self._tree[i] = self._fn(self._tree[i * 2 + 1], self._tree[i * 2 + 2])
                i -= 1

    def set(self, i, value):
        """
        i 番目に value を設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self._tree[x] = value

        while x > 0:
            x = (x - 1) // 2
            self._tree[x] = self._fn(self._tree[x * 2 + 1], self._tree[x * 2 + 2])

    def add(self, i, value):
        """
        もとの i 番目と value に fn を適用したものを i 番目に設定
        :param int i:
        :param value:
        :return:
        """
        x = self._size - 1 + i
        self.set(i, self._fn(self._tree[x], value))

    def get(self, from_i, to_i=None, k=0, L=None, r=None):
        """
        [from_i, to_i) に fn を適用した結果を返す
        :param int from_i:
        :param int to_i:
        :param int k: self._tree[k] が、[L, r) に fn を適用した結果を持つ
        :param int L:
        :param int r:
        :return:
        """
        if to_i is None:
            return self._tree[self._size - 1 + from_i]
        L = 0 if L is None else L
        r = self._size if r is None else r

        if from_i <= L and r <= to_i:
            return self._tree[k]

        if to_i <= L or r <= from_i:
            return None

        ret_L = self.get(from_i, to_i, k * 2 + 1, L, (L + r) // 2)
        ret_r = self.get(from_i, to_i, k * 2 + 2, (L + r) // 2, r)
        if ret_L is None:
            return ret_r
        if ret_r is None:
            return ret_L
        return self._fn(ret_L, ret_r)

    def __len__(self):
        return self._size


N, M = list(map(int, sys.stdin.readline().split()))
LRC = [list(map(int, sys.stdin.readline().split())) for _ in range(M)]

LRC.sort()
LRC = [(l - 1, r - 1, c) for l, r, c in LRC]
i = 0


dp = SegmentTree(N, fn=min, initial_values=[INF] * N)
dp.set(0, 0)
for pos in range(N):
    d = dp.get(pos, N)
    while i < M and LRC[i][0] == pos:
        l, r, c = LRC[i]
        dp.set(r, min(d + c, dp.get(r)))
        i += 1
ans = dp.get(N - 1)
if ans == INF:
    print(-1)
else:
    print(ans)

Solution (Python):
import sys


class AlgSegmentTreeMin:
    def __init__(self, n, default_value):
        self.Nelem = n
        self.default_value = default_value
        self.size = 1 << (n.bit_length())
        self.data = [default_value] * (2 * self.size)

    def build(self, raw_data):
        for i, x in enumerate(raw_data):
            self.data[self.size + i] = x
        for i in range(self.size - 1, 0, -1):
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)

    def update(self, i, x):
        i += self.size
        self.data[i] = x
        i >>= 1
        while i:
            x = self.data[i + i]
            y = self.data[i + i + 1]
            self.data[i] = min(x, y)
            i >>= 1

    def get_value(self, left, right):
        left += self.size
        right += self.size + 1
        x = self.default_value
        while left < right:
            if left & 1:
                y = self.data[left]
                x = min(x, y)
                left += 1
            if right & 1:
                right -= 1
                y = self.data[right]
                x = min(x, y)
            left >>= 1
            right >>= 1
        return x


def solve():
    input = sys.stdin.readline
    mod = 10 ** 9 + 7
    n, m = list(map(int, input().rstrip('\n').split()))
    stree = AlgSegmentTreeMin(n, 10 ** 15)
    stree.update(0, 0)
    lrc = [list(map(int, input().rstrip('\n').split())) for _ in range(m)]
    lrc.sort()
    for l, r, c in lrc:
        l -= 1
        r -= 1
        tm = stree.get_value(l, r)
        stree.update(r, min(tm + c, stree.get_value(r, r + 1)))
    mt = stree.get_value(n-1, n)
    print(mt if mt != stree.default_value else -1)


if __name__ == '__main__':
    solve()

Solution (Python):
from heapq import heappop, heappush
N, M = map(int, input().split())
V = [[] for _ in range(N)]
for i in range(1,N):
    V[i].append((i-1, 0))
for _ in range(M):
    l, r, c = map(int, input().split())
    V[l-1].append((r-1, c))
INF = float('inf')

q = [(0, 0)]
d = [INF] * N
d[0] = 0

while q:
    _, u = heappop(q)
    for v, c in V[u]:
        if d[v] > d[u] + c:
            d[v] = d[u] + c
            heappush(q, (d[v], v))

print(d[-1] if d[-1] != INF else -1)