787. Cheapest Flights Within K Stops

main.py

class Solution(object):
    def findCheapestPrice(self, n, flights, src, dst, k):
        # bellman-ford 
        p = [float('inf') for _ in range(n)]
        c = [float('inf') for _ in range(n)]
        p[src] = 0
        
        for i in range(k+1):
            for u, v, w in flights:
                c[v] = min(p[u]+w, c[v])
            p = copy.copy(c)
        
        return -1 if c[dst] == float('inf') else c[dst]