73 矩阵置零

https://leetcode.cn/leetbook/read/top-interview-questions-medium/xvpj16/

cost: 46m45s

class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size();
        int n = matrix[0].size();
        int flag = 0;
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (matrix[i][j] == 0) {
                    if (i == 0) {
                        flag |= 1;
                    }
                    if (j == 0) {
                        flag |= 2;
                    }
                    matrix[0][j] = 0;
                    matrix[i][0] = 0;
                }
            }
        }
        for (int i = 1; i < m; i++) {
            if (matrix[i][0] == 0) {
                for (int j = 0; j < n; j++) {
                    matrix[i][j] = 0;
                }
            }
        }
        for (int j = 1; j < n; j++) {
            if (matrix[0][j] == 0) {
                for (int i = 0; i < m; i++) {
                    matrix[i][j] = 0;
                }
            }
        }
        if (flag & 1) {
            for (int j = 0; j < n; j++) {
                matrix[0][j] = 0;
            }
        }
        if (flag & 2) {
            for (int i = 0; i < m; i++) {
                matrix[i][0] = 0;
            }
        }
    }
};