# 73 Set Matrix Zeroes – Medium

### Problem:

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

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?

### Thoughts:

The most tricky part of this problem is to do it in place.

The trick is to leverage the first row and the first column to serve as flag.

### Solutions:

``````public class Solution {
public void setZeroes(int[][] matrix) {
if (matrix == null || matrix.length ==0 || matrix[0].length == 0) {
return;
}
boolean row = false, column = false;
for (int i = 0; i < matrix.length; i ++) {
if (matrix[i][0] == 0) {
column = true;
break;
}
}
for (int j = 0; j < matrix[0].length; j ++) {
if (matrix[0][j] == 0) {
row = true;
break;
}
}
for (int i = 1; i < matrix.length; i ++) {
for (int j = 1; j < matrix[0].length; j ++) {
if (matrix[i][j] == 0) {
matrix[i][0] = 0;
matrix[0][j] = 0;
}
}
}
for (int i = 1; i < matrix.length; i ++) {
if (matrix[i][0] == 0) {
for (int j = 1; j < matrix[0].length; j ++) {
matrix[i][j] = 0;
}
}
}
for (int j = 1; j < matrix[0].length; j ++) {
if (matrix[0][j] == 0) {
for (int i = 1; i < matrix.length; i ++) {
matrix[i][j] = 0;
}
}
}
if (column == true) {
for (int i = 0; i < matrix.length; i ++) {
matrix[i][0] = 0;
}
}
if (row == true) {
for (int j = 0; j < matrix[0].length; j ++) {
matrix[0][j] = 0;
}
}
}//setZeroes
}
``````