negative_cycle.py

#Uses python3

import sys


def negative_cycle(adj, cost):
    #write your code here
    distance =[1001]*len(adj)
    distance[0]=0
    for _ in range(len(adj)-1):
        for vertex in range(len(adj)):
            for neighbor,weight in zip(adj[vertex],cost[vertex]):
                if distance[neighbor] > distance[vertex] + weight:
                        distance[neighbor] = distance[vertex] + weight

    for vertex in range(len(adj)):
        for neighbor, weight in zip(adj[vertex], cost[vertex]):
            if distance[neighbor] > distance[vertex] + weight:
                    return 1
    return 0


if __name__ == '__main__':
    input = sys.stdin.read()
    data = list(map(int, input.split()))
    n, m = data[0:2]
    data = data[2:]
    edges = list(zip(zip(data[0:(3 * m):3], data[1:(3 * m):3]), data[2:(3 * m):3]))
    data = data[3 * m:]
    adj = [[] for _ in range(n)]
    cost = [[] for _ in range(n)]
    for ((a, b), w) in edges:
        adj[a - 1].append(b - 1)
        cost[a - 1].append(w)
    print(negative_cycle(adj, cost))