Create FriendCircles.java

FriendCircles.java

@@ -0,0 +1,61 @@
+class UnionFind {
+    private int[] parents;
+    private int circleCount; 
+
+    public UnionFind(int n) {
+        parents = new int[n];
+        for (int i = 0; i < n; i++) {
+            parents[i] = i;
+        }
+    }
+
+    public int find(int x) {
+        if (parents[x] == x) {
+            return x;
+        }
+
+        return parents[x] = find(parents[x]);
+    }
+
+    public void union(int a, int b) {
+        int groupA = find(a);
+        int groupB = find(b);
+
+        if (groupA != groupB) {
+            parents[groupA] = groupB;
+            circleCount--;
+        }        
+    }
+
+    public void setCircleCount(int circleCount) {
+        this.circleCount = circleCount;
+    }
+
+    public int getCircleCount() {
+        return this.circleCount;    
+    }    
+}
+
+class Solution {
+    public int findCircleNum(int[][] M) {
+        if (M.length == 0 || M[0].length == 0) {
+            return 0;
+        }
+
+        int m = M.length;
+        int n = M[0].length;
+
+        UnionFind unionFind = new UnionFind(m * n);
+        unionFind.setCircleCount(m);
+
+        for (int i = 0; i < m; i++) {
+            for (int j = 0; j < n; j++) {
+                if (M[i][j] == 1 && i != j) {
+                    unionFind.union(i, j);        
+                }                
+            }            
+        }
+
+        return unionFind.getCircleCount();
+    }
+}