73. Set Matrix Zeroes
1. Description
Given an m x n integer matrix matrix, if an element is 0, set its entire row and column to 0’s.
You must do it in place.
2. Example
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]]
3. Constraints
- m == matrix.length
- n == matrix[0].length
- 1 <= m, n <= 200
- $-2^{31}$ <= matrix[i][j] <= $2^{31} - 1$
4. Solutions
Reuse first row column
m = matrix.size(), n = matrix.front().size()
Time complexity: O(mn)
Space complexity: O(1)
class Solution {
public:
void setZeroes(vector<vector<int>> &matrix) {
const int m = matrix.size(), n = matrix.front().size();
bool first_column_has_zero = false;
for (int i = 0; i < m; ++i) {
if (matrix[i][0] == 0) {
first_column_has_zero = true;
}
for (int j = 1; j < n; ++j) {
if (matrix[i][j] == 0) {
matrix[i][0] = matrix[0][j] = 0;
}
}
}
for (int i = m - 1; i >= 0; --i) {
for (int j = 1; j < n; ++j) {
if (matrix[i][0] == 0 || matrix[0][j] == 0) {
matrix[i][j] = 0;
}
}
if (first_column_has_zero) {
matrix[i][0] = 0;
}
}
}
};