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

Add JAVA solution for Question 323

Author: neetcode-gh

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;
+    }
+}