1.8 Zero Matrix

Using the first row and column to store that row and col’s state:
if there is a ‘0’ element matrix[i][0] = matrix[0][j] = 0.
And using a tmp variable (at here it’s called col0) to indicate the first element of each row, if it’s 0 then tmp = 0 or tmp = 1;
Finally, we set the matrix bottom up.

    void setZeroes(vector<vector<int>>& matrix){        int m = matrix.size(), n = matrix[0].size();        int col0 = 1;        for (int i = 0; i<m; ++i) {            if (matrix[i][0] == 0) col0 = 0;            for (int j = 0; j<n; ++j) {                if (!matrix[i][j]){                    matrix[i][0] = 0;                    matrix[0][j] = 0;                }            }        }        for (int i = m-1; i >= 0; --i) {            for (int j = n - 1; j >= 1; --j) {                if (!matrix[i][0] || !matrix[0][j]) matrix[i][j] = 0;            }            if (!col0) matrix[i][0] = 0;        }    }