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 Solution { /**The algorithm is simple. but we need to pay attention to the first row and first column. * @author Averill Zheng * @version 2014-06-15 * @since JDK 1.7 */ public void setZeroes(int[][] matrix) { int row = matrix.length; if(row > 0){ int column = matrix[0].length; //find if we need to set first row or first column to be zero boolean setRow = false; boolean setColumn = false; for(int i = 0; i < column; ++i){ if(matrix[0][i] == 0){ setRow = true; break; } } for(int i = 0; i < row; ++i){ if(matrix[i][0] == 0){ setColumn = true; break; } } for(int i = 1; i < row; ++i){ for(int j = 1; j < column; ++j){ if(matrix[i][j] == 0){ matrix[i][0] = 0; matrix[0][j] = 0; } } } //set zeros; for(int j = 1; j < column; ++j){ if(matrix[0][j] == 0){ for(int i = 1; i < row; ++i) matrix[i][j] = 0; } } for(int i = 1; i < row; ++i){ if(matrix[i][0] == 0){ for(int j = 1; j < column; ++j) matrix[i][j] = 0; } } if(setRow){ for(int i = 0; i < column; ++i) matrix[0][i] = 0; } if(setColumn){ for(int i = 0; i < row; ++i) matrix[i][0] = 0; } } } }