Merge pull request neetcode-gh#488 from hogo6002/patch-1

Add JAVA solution for Question 323

java/323-Number-of-Connected-Components-in-an-Undirected-Graph.java

@@ -0,0 +1,53 @@
+class Solution {
+ private int[] parent;
+ private int[] rank;
+
+ public int countComponents(int n, int[][] edges) {
+ parent = new int[n];
+ rank = new int[n];
+
+ for (int i = 0; i < n; i++) {
+ parent[i] = i;
+ rank[i] = 1;
+ } 
+
+ int result = n;
+ for (int i = 0; i < edges.length; i++) {
+ if (union(edges[i][0], edges[i][1]) == 1) {
+ result--;
+ }
+ }
+
+ return result;
+ }
+
+ private int find(int node) {
+ int result = node;
+
+ while (parent[result] != result) {
+ parent[result] = parent[parent[result]];
+ result = parent[result];
+ }
+
+ return result;
+ }
+
+ private int union(int n1, int n2) {
+ int p1 = this.find(n1);
+ int p2 = this.find(n2);
+
+ if (p1 == p2) {
+ return 0;
+ }
+
+ if (rank[p2] > rank[p1]) {
+ parent[p1] = p2;
+ rank[p2] += rank[p1];
+ } else {
+ parent[p2] = p1;
+ rank[p1] += rank[p2];
+ }
+
+ return 1;
+ }
+}