Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place. Follow up: Did you use extra space? A straight forward solution using O(mn) space is probably a bad idea. A simple improvement uses O(m + n) space, but still not the best solution. Could you devise a constant space solution? http://leetcode.com/onlineju…

leetcode_set_matrix_zeros.cpp

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