Leetcode 261. Graph Valid Tree

Given n nodes labeled from 0 to n - 1 and a list of undirected edges (each edge is a pair of nodes), write a function to check whether these edges make up a valid tree.

For example:

Given n = 5 and edges = [[0, 1], [0, 2], [0, 3], [1, 4]], return true.

Given n = 5 and edges = [[0, 1], [1, 2], [2, 3], [1, 3], [1, 4]], return false.

Note: you can assume that no duplicate edges will appear in edges. Since all edges are undirected, [0, 1] is the same as [1, 0]and thus will not appear together in edges.

    public boolean validTree(int n, int[][] edges) {        if (edges.length != n - 1) return false;        int[] nums = new int[n];        Arrays.fill(nums, -1);        for (int i = 0; i < edges.length; i++) {            int x = find(nums, edges[i][0]);            int y = find(nums, edges[i][1]);            if (x == y) return false;            nums[x] = y;        }        return true;    }        private int find(int nums[], int i) {        if (nums[i] == -1) return i;        return find(nums, nums[i]);    }