LeetCode OJ 073Set Matrix Zeroes

Posted 2022-11-16 xujian_2014

题目链接:https://leetcode.com/problems/set-matrix-zeroes/

题目：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?

解题思路：保存行和列为0的索引，改变该行和该列上的所有数为0即可，实现代码如下所示：

public class Solution
	
	public void setZeroes(int[][] matrix) 
	
		int m=matrix.length; //行数
        if(m==0)
        	return ;
        int n=matrix[0].length; //列数
        
        List<Integer> a=new ArrayList<Integer>();  //存放所有的行中值为0的索引
        List<Integer> b=new ArrayList<Integer>();  //存放所有的列中值为0的索引
        for (int i = 0; i < m; i++)
		
			for (int j = 0; j < n; j++)
			
				if(matrix[i][j]==0)
				
					a.add(i);
					b.add(j);
				
			
		
        //将所有行上值为0的那一行的值都改为0
        for(int i:a)
        
        	for(int j=0;j<n;j++)
        	
        		matrix[i][j]=0;
        	
        
        //将所有列上值为0的那一列的值都改为0
        for(int i:b)
        
        	for(int j=0;j<m;j++)
        	
        		matrix[j][i]=0;