Graph Valid Tree

 1 public class Solution {
 2     private int[] parent;
 3     public boolean validTree(int n, int[][] edges) {
 4         if (n < 2) {
 5             return true;
 6         }
 7         parent = new int[n];
 8         for (int i = 0; i < n; i++) {
 9             parent[i] = i;
10         }
11         
12         for (int[] edge : edges) {
13             int indexA = findParent(edge[0]);
14             int indexB = findParent(edge[1]);
15             if (indexA == indexB) {
16                 return false;
17             }
18             if (indexA < indexB) {
19                 parent[indexB] = indexA;
20             } else if (indexA > indexB) {
21                 parent[indexB] = parent[indexA];
22             }
23         }
24         int count = 0;
25         for (int i = 0; i < n; i++) {
26             if (parent[i] == i) {
27     private int findParent(int i) {
28         while (i != parent[i]) {
29             parent[i] = parent[parent[i]];
30             i = parent[i];
31         }
32         return i;
33     }
34 }

1. No circle : parent index not equal

2. Only one root.

posted on 2016-07-07 15:36 keepshuatishuati 阅读(158) 评论(0) 编辑收藏举报