Floyd Warshall - all nodes to all nodes distance

#Floyd warshall: It helps you to find the distance bw all node to all the other nodes unlike the Bellman and Djktra where we have a fixed source.
#it works with directed only, so convert undirected to directed.
#Negative Cycle detection: if the distance between ith node to the ith node is less than 0, It means there is a negative cycle.

#User function template for Python
inf=pow(10,8)
class Solution:
    def floydWarshall(self, dist):
        n=len(dist)

        for via in range(n):
            for src in range(n):
                for dest in range(n):
                    if dist[src][via]==inf or dist[via][dest]==inf: #There is no point of one distance of two route is infinity.
                        continue
                    dist[src][dest]=min(dist[src][dest], (dist[src][via]+dist[via][dest]))
                    if dist[src][dest]<0 and src==dest: #This one avoid the negative cycle, because negative cycle will keep reducing the distance of a node to the same node
                        return [-1]
        return dist