【LeetCode OJ 073】Set Matrix Zeroes淺析

【LeetCode OJ 073】Set Matrix Zeroes淺析

題目：Given amxnmatrix, if an element is 0, set its entire row and column to 0. Do it in place.

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?

解題思路：保存行和列為0的索引，改變該行和該列上的所有數為0即可，實現代碼如下所示：

public class Solution
{	
	public void setZeroes(int[][] matrix) 
	{
		int m=matrix.length; //行數
        if(m==0)
        	return ;
        int n=matrix[0].length; //列數
        
        List a=new ArrayList();  //存放所有的行中值為0的索引
        List b=new ArrayList();  //存放所有的列中值為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);
				}
			}
		}
        //將所有行上值為0的那一行的值都改為0
        for(int i:a)
        {
        	for(int j=0;j