73. Set Matrix Zeroes (Medium)
https://leetcode.com/problems/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?
Solutions
class Solution {
public void setZeroes(int[][] matrix) {
if (matrix == null || matrix.length == 0) {
return;
}
int tmp = 1690664872;
int row = matrix.length;
int col = matrix[0].length;
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
if (matrix[i][j] != 0) {
continue;
}
// To reach here, matrix[i][j] is 0
// do not turn values on same row/column to 0, it will bring in consequent
// influence for followup processing.
for (int x = 0; x < row; x++) {
// do not modify the cell if original value is 0
if (matrix[x][j] == 0) {
continue;
}
matrix[x][j] = tmp;
}
for (int y = 0; y < col; y++) {
// do not modify the cell if original value is 0
if (matrix[i][y] == 0) {
continue;
}
matrix[i][y] = tmp;
}
}
}
// reset the turned values to 0
for (int i = 0; i < row; i++) {
for (int j = 0; j < col; j++) {
if (matrix[i][j] == tmp) {
matrix[i][j] = 0;
}
}
}
}
}