Problem: 2063C - Remove Exactly Two
Language: PyPy 3-64

Previous submission (verdict: Wrong answer on test 4):

t = int(input())

for x in range(t):
    n = int(input())
    edges = []
    adj_list = []

    for y in range(n+1):
        adj_list.append([])

    for e in range(n-1):
        a,b = list(map(int, input().split(" ")))
        
        adj_list[a].append(b)
        adj_list[b].append(a)


    for i in range(2):
        most_edges = 0
        most_edges_node = 1
        for node in range(1, n+1):
            if adj_list[node] != None:
                if len(adj_list[node]) >= most_edges:
                    most_edges = len(adj_list[node])
                    most_edges_node = node

        for node in adj_list[most_edges_node]:
            adj_list[node].remove(most_edges_node)

        adj_list[most_edges_node] = None

    count_cc = 0
    connected = {}
    v = 1
    for node in range(1, n+1):
        if adj_list[node] != None and not node in connected:
            queue = [node]

            while len(queue) > 0:
                curr = queue.pop()
                connected[curr] = count_cc
                for adj_node in adj_list[curr]:
                    if not adj_node in connected:
                        queue.append(adj_node)
                        connected[adj_node] = count_cc

            count_cc += 1

    print(count_cc)


Submission (verdict: Runtime error on test 2):
t = int(input())

for x in range(t):
    n = int(input())
    edges = []
    adj_list = []

    for y in range(n+1):
        adj_list.append([])

    for e in range(n-1):
        a,b = list(map(int, input().split(" ")))
        
        adj_list[a].append(b)
        adj_list[b].append(a)


    for i in range(2):
        cnt_max_edges = 0
        max_edges = []
        for node in range(1, n+1):
            if adj_list[node] != None:
                if len(adj_list[node]) > cnt_max_edges:
                    cnt_max_edges = len(adj_list[node])
                    max_edges = [node]
                elif len(adj_list[node]) == cnt_max_edges:
                    max_edges.append(node)

        # print("pass")
        if len(max_edges) <= 2 or i == 1:
            max_edges = [max_edges[0]]
        else:
            f = False
            for idx1 in range(0, len(max_edges)):
                # print(max_edges)
                # print(max_edges[idx1])
                if f: break
                for idx2 in range(1, len(max_edges)):
                    if f: break
                    if not max_edges[idx2] in adj_list[max_edges[idx1]]:
                        max_edges = [max_edges[idx1], max_edges[idx2]]
                        f = True

        for most_edges_node in max_edges:
            for node in adj_list[most_edges_node]:
                adj_list[node].remove(most_edges_node)

            adj_list[most_edges_node] = None

        if len(max_edges) >= 2:
            break

    count_cc = 0
    connected = {}
    v = 1
    for node in range(1, n+1):
        if adj_list[node] != None and not node in connected:
            queue = [node]

            while len(queue) > 0:
                curr = queue.pop()
                connected[curr] = count_cc
                for adj_node in adj_list[curr]:
                    if not adj_node in connected:
                        queue.append(adj_node)
                        connected[adj_node] = count_cc

            count_cc += 1

    print(count_cc)