leetcode-第5周双周赛-1135-最低成本联通所有城市

方法一：

class Solution:
    def minimumCost(self, N: int, conections: List[List[int]]) -> int:
        def find(i):
            if father[i]==i:
                return i
            else:
                father[i]=find(father[i])
                return father[i]

        conn=sorted(conections,key=lambda item:item[2])
        visited=[]
        res=0
        father=[i for i in range(N+1)]
        for item in conn:
            i,j=item[0],item[1]
            cost=item[2]
            fi,fj=find(i),find(j)
            if fi==fj:
                continue
            res+=cost
            father[fi]=fj
            visited.append((i,j))
        return res if len(visited)==N-1 else -1