73. Set Matrix Zeroes


Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0's, and return the matrix.

You must do it in place.

 

Example 1:

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

Example 2:

Input: matrix = [[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]]

 

Constraints:

  • m == matrix.length
  • n == matrix[0].length
  • 1 <= m, n <= 200
  • -231 <= matrix[i][j] <= 231 - 1

 

Follow up:

  • A straightforward 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?

The solution to the above question 

class Solution {
public:
    void setZeroes(vector<vector<int>>& v) {
        bool row=false;
        bool col=false;
        for(int i=0; i<v.size(); i++){
            for(int j=0; j<v[0].size(); j++){
                if(v[i][j]==0){
                    v[0][j]=0;
                    v[i][0]=0;
                    if(i==0){
                        row=true;
                    }
                    if(j==0){
                        col=true;
                    }
                }
            }
        }
        for(int i=1; i<v[0].size(); i++){
            if(v[0][i]==0){
                for(int j=0; j<v.size(); j++){
                    v[j][i]=0;
                }
            }
        }
        for(int i=1; i<v.size(); i++){
            if(v[i][0]==0){
                for(int j=0; j<v[0].size(); j++){
                    v[i][j]=0;
                }
            }
        }
        if(row){
            for(int i=0; i<v[0].size(); i++){
                v[0][i]=0;
            }
        }
        if(col){
            for(int i=0; i<v.size(); i++){
                v[i][0]=0;
            }
        }
        
         for(int i=0; i<v.size(); i++){
            for(int j=0; j<v[0].size(); j++){
                {
                    cout<<v[i][j]<<" ";
                }
            }
             cout<<endl;
        }
    }
};