Description
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 start to vertex end.
Given edges and the integers n, start, and end, return true if there is a valid path from start to end, or false otherwise.
有一个具有 n个顶点的 双向 图，其中每个顶点标记从 0 到 n - 1（包含 0 和 n - 1）。图中的边用一个二维整数数组 edges 表示，其中 edges[i] = [ui, vi] 表示顶点 ui 和顶点 vi 之间的双向边。 每个顶点对由 最多一条 边连接，并且没有顶点存在与自身相连的边。
请你确定是否存在从顶点 start 开始，到顶点 end 结束的 有效路径 。
给你数组 edges 和整数 n、start和end，如果从 start 到 end 存在 有效路径 ，则返回 true，否则返回 false 。
Examples
# Example 1
Input: n = 3, edges = [[0,1],[1,2],[2,0]], start = 0, end = 2
Output: true
Explanation: There are two paths from vertex 0 to vertex 2:
- 0 → 1 → 2
- 0 → 2
# Example 2
Input: n = 6, edges = [[0,1],[0,2],[3,5],[5,4],[4,3]], start = 0, end = 5
Output: false
Explanation: There is no path from vertex 0 to vertex 5.Solution
首先使用提供的边，基于顶点收集该定点相邻的顶点。
再从目标起点出发，对相邻及其相邻的顶点进行查询，最后查看终点是否被查询。
/**
* @param {number} n
* @param {number[][]} edges
* @param {number} start
* @param {number} end
* @return {boolean}
*/
var validPath = function(n, edges, start, end) {
if(start === end) return true;
let globals = {}, visited = {};
// 收集各个顶点的边
for(let i = 0; i < edges.length; i++) {
let u = edges[i][0], v = edges[i][1];
!globals[u] ? globals[u] = [v] : globals[u].push(v);
!globals[v] ? globals[v] = [u] : globals[v].push(u);
}
// 从起点开始递归查询子顶点经过的路径
dfs(start, visited);
// 经过的点都被做上查询标记
// 若终点无标记则说明从未被访问，即无路径抵达终点
return visited[end] ? true : false;
function dfs(vertex, visited) {
// 已查询顶点标记
if(visited[vertex]) return;
visited[vertex] = true;
for(let child of globals[vertex]) {
dfs(child, visited);
}
}
};Result
Accepted
25/25 cases passed (1124 ms)
Your runtime beats 13.18 % of javascript submissions
Your memory usage beats 22.08 % of javascript submissions (157.1 MB)
