73. Set Matrix Zeroes

难度: Medium

题目描述

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.

 

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]]

 

Constraints:

• m == matrix.length
• n == matrix[0].length
• 1 <= m, n <= 200
• -231 <= matrix[i][j] <= 231 - 1

 

Follow up:

• A straightforward 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?

解题思路

代码实现

解决方案

java

class Solution {
    public void setZeroes(int[][] matrix) {

        boolean rowFlag = false;
        boolean colFlag = false;
        for (int i = 0; i < 1; i++) {
            for (int j = 0; j < matrix[0].length; j++) {

                if (matrix[i][j] == 0) {
                    rowFlag = true;
                }

            }
        }
        for (int i = 0; i < matrix.length; i++) {
            for (int j = 0; j < 1; j++) {

                if (matrix[i][j] == 0) {
                    colFlag = true;
                }

            }
        }
        for (int i = 1; i < matrix.length; i++) {
            for (int j = 1; j < matrix[0].length; j++) {
                if (matrix[i][j] == 0) {
                    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 (rowFlag) {
            for (int i = 0; i < 1; i++) {
                for (int j = 0; j < matrix[0].length; j++) {

                    matrix[i][j] = 0;

                }
            }
        }
        if (colFlag) {
            for (int i = 0; i < matrix.length; i++) {
                for (int j = 0; j < 1; j++) {

                    matrix[i][j]=0;

                }
            }
        }

    }
}