[Leetcode] Set Matrix Zeroes

Given a m x n matrix, if an element is 0, set its entire row and column to 0. Do it in place.

如果不用额外空间的话，可以把第一行与第一列作为标记行与标记列，但是得先确定第一行与第一列本身要不要设为0。

class Solution {
public:
    void setZeroes(vector<vector<int> > &matrix) {
        if (matrix.size() < 1) return;
        int row = matrix.size(), col = matrix[0].size();
        bool r0 = false, c0 = false;
        for (int i = 0; i < row; ++i) {
            if (matrix[i][0] == 0) {
                c0 = true; break;
            }
        }
        for (int j = 0; j < col; ++j) {
            if (matrix[0][j] == 0) {
                r0 = true; break;
            }
        }
        for (int i = 1; i < row; ++i) {
            for (int j = 1; j < col; ++j) {
                matrix[i][0] = (matrix[i][j] == 0) ? 0 : matrix[i][0];
                matrix[0][j] = (matrix[i][j] == 0) ? 0 : matrix[0][j];
            }   
        }
        for (int i = 1; i < row; ++i) {
            for (int j = 1; j < col; ++j) {
                 matrix[i][j] = (matrix[i][0] == 0) ? 0 : matrix[i][j];
                 matrix[i][j] = (matrix[0][j] == 0) ? 0 : matrix[i][j];
            }   
        }
        for (int i = 0; i < row && c0; ++i)  matrix[i][0] = 0;
        for (int j = 0; j < col && r0; ++j)  matrix[0][j] = 0;
    }
};