每日一道算法题之并查集之移除最多的同行或同列石头

import java.util.HashMap;

class Solution {

    public static HashMap<Integer, Integer> row = new HashMap<>();
    public static HashMap<Integer, Integer> col = new HashMap<>();

    public static int MAXN = 1001;
    public static int[] f = new int[MAXN];

    public static int set = MAXN;

    public static void build(int n) {
        row.clear();
        col.clear();
        for (int i = 0; i < n; i++) {
            f[i] = i;

        }
        set = n;
    }

    public static int find(int i) {
        if (f[i] != i) {
            f[i] = find(f[i]);
        }
        return f[i];
    }

    public static void union(int i, int j) {
        int f_i = find(i);
        int f_j = find(j);
        if (f_i != f_j) {
            f[f_i] = f_j;
            set--;
        }
    }

    public int removeStones(int[][] stones) {
        int n = stones.length;

        build(n);

        for (int i = 0; i < n; i++) {

            if (row.containsKey(stones[i][0])) {
                // 当前行已经有数了。可以合并。
                union(i, row.get(stones[i][0]));
            } else {
                row.put(stones[i][0], i);
            }

            if (col.containsKey(stones[i][1])) {
                union(i, col.get(stones[i][1]));

            } else {
                col.put(stones[i][1], i);
            }

        }

        return n - set;

    }
}