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SetMatrixZeroes73.java
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SetMatrixZeroes73.java
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/**
* Given a m x n matrix, if an element is 0, set its entire row and column
* to 0. Do it in place.
*
* Follow up:
* 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?
*/
public class SetMatrixZeroes73 {
public void setZeroes(int[][] matrix) {
boolean[] rows = new boolean[matrix.length];
boolean[] cols = new boolean[matrix[0].length];
for (int i=0; i<matrix.length; i++) {
for (int j=0; j<matrix[0].length; j++) {
if (matrix[i][j] == 0) {
rows[i] = true;
cols[j] = true;
}
}
}
for (int i=0; i<matrix.length; i++) {
for (int j=0; j<matrix[0].length; j++) {
if (rows[i] || cols[j]) matrix[i][j] = 0;
}
}
}
/**
* https://leetcode.com/problems/set-matrix-zeroes/discuss/26008/My-AC-java-O(1)-solution-(easy-to-read)
*/
public void setZeroes2(int[][] matrix) {
boolean fr = false,fc = false;
for(int i = 0; i < matrix.length; i++) {
for(int j = 0; j < matrix[0].length; j++) {
if(matrix[i][j] == 0) {
if(i == 0) fr = true;
if(j == 0) fc = true;
matrix[0][j] = 0;
matrix[i][0] = 0;
}
}
}
for(int i = 1; i < matrix.length; i++) {
for(int j = 1; j < matrix[0].length; j++) {
if(matrix[i][0] == 0 || matrix[0][j] == 0) {
matrix[i][j] = 0;
}
}
}
if(fr) {
for(int j = 0; j < matrix[0].length; j++) {
matrix[0][j] = 0;
}
}
if(fc) {
for(int i = 0; i < matrix.length; i++) {
matrix[i][0] = 0;
}
}
}
}