Leetcode: Number of Connected Components in an Undirected Graph

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 find the number of connected components in an undirected graph.

Example 1:
0          3
|          |
1 --- 2    4
Given n = 5 and edges = [[0, 1], [1, 2], [3, 4]], return 2.

Example 2:
0           4
|           |
1 --- 2 --- 3
Given n = 5 and edges = [[0, 1], [1, 2], [2, 3], [3, 4]], return 1.

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 class Solution {
public int countComponents(int n, int[][] edges) {
unionFind uf = new unionFind(n);
for (int[] edge : edges) {
if (!uf.isConnected(edge[0], edge[1])) {
uf.union(edge[0], edge[1]);
}
}
return uf.findCount();
}

public class unionFind{
int[] ids;
int count;

public unionFind(int num) {
this.ids = new int[num];
for (int i=0; i<num; i++) {
ids[i] = i;
}
this.count = num;
}

public int find(int i) {
return ids[i];
}

public void union(int i1, int i2) {
int id1 = find(i1);
int id2 = find(i2);
if (id1 != id2) {
for (int i=0; i<ids.length; i++) {
if (ids[i] == id2) {
ids[i] = id1;
}
}
count--;
}
}

public boolean isConnected(int i1, int i2) {
return find(i1)==find(i2);
}

public int findCount() {
return count;
}
}
}