AtCoder Beginners Contest 過去問チャレンジ 10 - Qiita

from sys import stdin N, M = map(int, stdin.readline().split()) links = [[] for _ in range(N + 1)] for _ in range(M): L, R, D = map(int, stdin.readline().split()) links[L].append((R, D)) links[R].append((L, -D)) t = [None] * (N + 1) for i in range(1, N + 1): if t[i] is not None: continue t[i] = 0 s = [i] while s: j = s.pop() for k, l in links[j]: if t[k] is None: t[k] = t[j] + l s.append(k) else: