[LeetCode] 947. Most Nodes Removed

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]]
Output: 5
Example 2:

Input: stones = [[0,0],[0,2],[1,1],[2,0],[2,2]]
Output: 3
Example 3:

Input: stones = [[0,0]]
Output: 0

Note:

1 <= stones.length <= 1000
0 <= stonesi < 10000

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]);
    }
}