Leetcode 73. 矩阵置零

先确认好哪几行哪几列要变0【标志保存在行/列首位】，注意0行0列标志重叠，特殊处理

class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int m = matrix.size(), n = m == 0 ? 0 : matrix[0].size(), h0 = 0, l0 = 0;
        for (int i = 0; i<m; ++i)
            for (int j = 0; j<n; ++j)
                if (matrix[i][j] == 0) {
                    matrix[i][0] = matrix[0][j] = 0;
                    if (i == 0) h0 = 1;
                    if (j == 0) l0 = 1;
                }
        for (int i = 1; i<m; ++i)
            if (!matrix[i][0]) {
                for (int j = 1; j<n; ++j)
                    matrix[i][j] = 0;
            }
        for (int j = 1; j<n; ++j)
            if (!matrix[0][j]) {
                for (int i = 1; i<m; ++i)
                    matrix[i][j] = 0;
            }
        if (h0) for (int j = 1; j<n; ++j)//0行为0
                matrix[0][j] = 0;
        if (l0) for (int i = 1; i<m; ++i)//0列为0
                matrix[i][0] = 0;
    }
};