2397. Maximum Rows Covered by Columns

You are given a 0-indexed m x n binary matrix mat and an integer cols, which denotes the number of columns you must choose.

A row is covered by a set of columns if each cell in the row that has a value of 1 also lies in one of the columns of the chosen set.

Return the maximum number of rows that can be covered by a set of cols columns.

class Solution {
public:
    int maximumRows(vector<vector<int>>& mat, int cols) {
        int res = 0, n = mat.size(), m = mat[0].size();
        for(int mask = 0; mask < (1<<m); mask++) {
            if(__builtin_popcount(mask) != cols) continue;
            int now = 0;
            for(int i = 0; i < n; i++) {
                bool pick = true;
                for(int j = 0; j < m; j++) {
                    if(mask & (1<<j)) continue;
                    if(mat[i][j]) pick = false;
                    if(!pick) break;
                }
                if(pick) now++;
            }
            res = max(res,now);
        }
        return res;
    }
};