lintcode-medium-Set Matrix Zeroes
2016-04-06 02:46
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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.
Example
Given a matrix
return
[
[0,2],
[0,0]
]
Challenge
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?
Example
Given a matrix
[ [1,2], [0,3] ],
return
[
[0,2],
[0,0]
]
Challenge
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 Solution { /** * @param matrix: A list of lists of integers * @return: Void */ public void setZeroes(int[][] matrix) { // write your code here if(matrix == null || matrix.length == 0 || matrix[0] == null || matrix[0].length == 0) return; int m = matrix.length; int n = matrix[0].length; boolean first_col = false; boolean first_row = false; for(int i = 0; i < m; i++) if(matrix[i][0] == 0){ first_col = true; break; } for(int i = 0; i < n; i++) if(matrix[0][i] == 0){ first_row = true; break; } for(int i = 1; i < m; i++){ for(int j = 1; j < n; j++){ if(matrix[i][j] == 0){ matrix[i][0] = 0; matrix[0][j] = 0; } } } for(int i = 1; i < n; i++){ if(matrix[0][i] == 0){ for(int j = 0; j < m; j++) matrix[j][i] = 0; } } for(int i = 1; i < m; i++){ if(matrix[i][0] == 0){ for(int j = 0; j < n; j++) matrix[i][j] = 0; } } if(first_col){ for(int i = 0; i < m; i++) matrix[i][0] = 0; } if(first_row){ for(int i = 0; i < n; i++) matrix[0][i] = 0; } return; } }
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