被列覆盖的最多行数

思路

1、使用回溯算法，不断的尝试覆盖numselect行数

2、找到最大覆盖行数

代码

import java.math.BigDecimal;
import java.util.*;
import java.util.stream.Collectors;

public class Main {
    public static void main(String[] args) {
        Solution solution = new Solution();
        int res = solution.maximumRows(new int[][]{
                {0,0,0,1},
                {0,1,0,1},
                {0,0,0,1},
                {0,1,0,1},

        }, 1);

        System.out.println(res);

    }

}

class Solution {
    int max;
    public int maximumRows(int[][] matrix, int numSelect) {
        if (matrix[0].length <= numSelect){
            return matrix.length;
        }

        int[] row = new int[matrix[0].length];
        for (int i = 0; i < row.length; i++) {
            row[i] = i;
        }

        calMaxRows(row, 0, numSelect, matrix);

        return max;
    }

    private void calMaxRows(int[] row, int index, int numSelect, int[][] matrix) {
        if (index == numSelect){
            max = Math.max(max, calRow(row, numSelect, matrix));
            return;
        }

        for (int i = index; i < row.length; i++) {
            swap(index, i, row);
            calMaxRows(row, index + 1, numSelect, matrix);
            swap(i, index, row);
        }

    }

    private void swap(int i, int j, int[] row) {
        int temp = row[i];
        row[i] = row[j];
        row[j] = temp;
    }


    private int calRow(int[] rows, int numSelect, int[][] matrix) {
        HashSet<Integer> selectRows = new HashSet<>();
        for (int i = 0; i < numSelect; i++) {
            selectRows.add(rows[i]);
        }

        int res = 0;
        for (int[] ints : matrix) {
            boolean flag = true;
            for (int col = 0; col < matrix[0].length; col++) {
                if (selectRows.contains(col)) {
                    continue;
                }
                if (ints[col] != 0) {
                    flag = false;
                    break;
                }
            }
            if (flag) {
                res++;
            }
        }
        return res;
    }


}