1971. Find if Path Exists in Graph

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#算法

文章介绍如何使用Union-Find算法检测从source到destination在带有双向边的n个节点图中是否存在路径。

1971. Find if Path Exists in Graph

There is a bi-directional graph with n vertices, where each vertex is labeled from 0 to n - 1 (inclusive). The edges in the graph are represented as a 2D integer array edges, where each edges[i] = [ui, vi] denotes a bi-directional edge between vertex ui and vertex vi. Every vertex pair is connected by at most one edge, and no vertex has an edge to itself.

You want to determine if there is a valid path that exists from vertex source to vertex destination.

Given edges and the integers n, source, and destination, return true if there is a valid path from source to destination, or false otherwise.

Union-Find：

class Solution:   
    def validPath(self, n: int, edges: List[List[int]], source: int, destination: int) -> bool:
        p = [i for i in range(n)]#每个i的根

        def find(i):#找根
            if p[i] != i:
                p[i] = find(p[i])
            return p[i]

        for u, v in edges:
            p[find(u)] = find(v)
        return find(source) == find(destination) #是否同根