unioning the points on same row or same column

Author: Arjiit

UnionFind/removeStones.java

@@ -0,0 +1,53 @@
+class Solution {
+    public int removeStones(int[][] stones) {
+        UnionFind uf = new UnionFind(stones.length);
+        for (int i=0; i<stones.length; i++) { // comparing any two points from the stones array
+            for (int j=i+1; j< stones.length; j++) {
+                if (stones[i][0] == stones[j][0] || stones[i][1] == stones[j][1]) { // same row or same column for both the points
+                    uf.union(i, j); //unioning the points
+                }
+            }
+        }
+        return stones.length - uf.count;
+    }
+}
+
+class UnionFind {
+    int count;
+    int[] parent;
+    int[] size; // used for union by rank for optimization
+    
+    public UnionFind(int n) {
+        this.count = n;
+        parent = new int[n];
+        size = new int[n];
+        
+        for (int i=0; i<n; i++) {
+            parent[i] = i;
+        }
+    }
+    
+    public int find(int x) {
+        while (parent[x] != x) {
+            x = parent[x];
+        }
+        return x;
+    }
+    
+    public void union(int p, int q) {
+        int pParent = find(p);
+        int qParent = find(q);
+        if (pParent == qParent) {
+            return;
+        }
+        
+        if (size[pParent] <= size[qParent]) { // union by rank, higher size ones becomes the overall parent for the smaller ones as well.
+            parent[pParent] = qParent;
+            size[qParent]++;
+        } else {
+            parent[qParent] = pParent;
+            size[pParent]++;
+        }
+        count--; // every time we union, connected components decreases by 1
+    }
+}