73. 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.

Example 1:

Input: 
[
  [1,1,1],
  [1,0,1],
  [1,1,1]
]
Output: 
[
  [1,0,1],
  [0,0,0],
  [1,0,1]
]

Example 2:

Input: 
[
  [0,1,2,0],
  [3,4,5,2],
  [1,3,1,5]
]
Output: 
[
  [0,0,0,0],
  [0,4,5,0],
  [0,3,1,0]
]

Follow up:

• 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?

 

my code:

class Solution {
public:
    void setZeroes(vector<vector<int>>& matrix) {
        int row = matrix.size();
        int col = matrix[0].size();
        vector<int> r;
        vector<int> c;
        for (int i = 0; i < row; ++i) {
            for (int j = 0; j < col; ++j) {
                if (matrix[i][j] == 0) {
                    r.push_back(i);
                    c.push_back(j);
                }
                    
            }
        }
        for (int i = 0; i < r.size(); ++i) {
            int x = r[i];
            int y = c[i];
            for (int j = 0; j < col; ++j) {
                matrix[x][j] = 0;
            }
            for (int j = 0; j < row; ++j) {
                matrix[j][y] = 0;
            }
        }
    }
};

Runtime: 36 ms, faster than 90.90% of C++ online submissions for Set Matrix Zeroes.