Connect cities

from collections import deque
n, m = map(int, input().split())

edges = [[0]*n for i in range(n)]

for i in range(m):
    a, b = map(int, input().split())
    edges[a-1][b-1] = 1
    edges[b-1][a-1] = 1

c = 0
clique = [-1] * n


def bfs(v):
    queue = deque([v])
    while queue:
        node = queue.popleft()
        for w in range(n):
            if edges[node][w] and clique[w] == -1:
                clique[w] = clique[v]
                queue.append(w)


for v in range(n):
    if clique[v] == -1:
        clique[v] = c
        c += 1
        bfs(v)

clique_sorted = [(clique[i], (i + 1)) for i in range(n)]
clique_sorted.sort()
print(c - 1)
i = 1
while i < n:
    if clique_sorted[i][0] != clique_sorted[i - 1][0]:
        print(clique_sorted[i][1], clique_sorted[i - 1][1])
    i += 1

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: ACCEPTED

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: RUNTIME ERROR

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: RUNTIME ERROR

Test 12

Verdict: ACCEPTED