Problem

On a 2D plane, we place stones at some integer coordinate points. Each coordinate point may have at most one stone.

Now, a move consists of removing a stone that shares a column or row with another stone on the grid.

What is the largest possible number of moves we can make?

Example 1:

Input: stones = [[0,0],[0,1],[1,0],[1,2],[2,1],[2,2]]

Input: stones = [[0,0],[0,2],[1,1],[2,0],[2,2]]

Input: stones = [[0,0]]

Note:

1 <= stones.length <= 1000

Solution

class Solution {    public int removeStones(int[][] stones) {        int m = stones.length;        int[] parents = new int[m];        for (int i = 0; i < m; i++) {            parents[i] = i;        }        int count = 0;        for (int i = 0; i < m; i++) {            for (int j = i+1; j < m; j++) {                if (stones[j][0] == stones[i][0] || stones[j][1] == stones[i][1]) {                    int p1 = find(parents, i);                    int p2 = find(parents, j);                    parents[p1] = p2;                    if (p1 != p2) {                        count++;                    }                }            }        }        return count;    }    private int find(int[] parents, int i) {        if (parents[i] == i) return i;        else return find(parents, parents[i]);    }}