221. Maximal Square

来源：互联网发布：济南市社保查询软件编辑：程序博客网时间：2024/05/21 14:28

Given a 2D binary matrix filled with 0's and 1's, find the largest square containing all 1's and return its area.

For example, given the following matrix:

1 0 1 0 01 0 1 1 11 1 1 1 11 0 0 1 0

Return 4.

Credits:
Special thanks to @Freezen for adding this problem and creating all test cases.

Subscribe to see which companies asked this question

更好的方法：每个点填以这个点为左上角的最大方格。当一个点本身为1，同时下右和下右三个点都至少为n时，这个点给n+1

public class Solution {    private int maxLen(char[][] m,int l,int i,int j){//判断当前点最大方格，至少边长l        for(int x = i;x<i+l;x++){            for(int y = j; y< j+l;y++){                if(m[x][y]=='0')return 0;            }        }        while(i+l<m.length&&j+l<m[0].length){            for(int x = i;x<=i+l;x++){                if(m[x][j+l]=='0')return l;            }            for(int y = j;y<=j+l;y++){                if(m[j+l][y]=='0')return l;            }            l++;        }        return l;    }    public int maximalSquare(char[][] matrix) {        int hang = matrix.length;        if (hang==0)return 0;        int lie = matrix[0].length;        int maxl = 0;        // for(int i = 0;i<hang - maxl;i++){        //     for(int j =0;j< lie - maxl;j++){                        //     }        // }        for(int i = hang-1;i>=0;i--){            for(int j = lie-1-maxl;j>=0;j--){                if(matrix[i][j]=='1'){                    int a = maxLen(matrix,maxl+1,i,j);                    if(a>maxl)maxl=a;                    if(i>hang-1-maxl){i=hang-maxl-1;j=lie-maxl;if(i<0)break;}//下一轮进j=lie-maxl-1                }            }        }        return maxl*maxl;    }}

0 0