221. Maximal Square

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LeetCode

DP: dp(i,j)=min(dp(i−1,j),dp(i−1,j−1),dp(i,j−1))+1

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class Solution {
    public int maximalSquare(char[][] matrix) {
        if(matrix.length==0) return 0;
        
        int rowNum=matrix.length;
        int colNum=matrix[0].length;
        int[][] dp=new int[rowNum+1][colNum+1];
        int maxEdgeLen=0;
        
        // i: length of row; j: length of colomn.
        for(int i=1;i<=rowNum;i++){
            for(int j=1;j<=colNum;j++){
                if(matrix[i-1][j-1]=='1'){
                    dp[i][j]=Math.min(Math.min(dp[i-1][j],dp[i][j-1]),dp[i-1][j-1])+1;
                    maxEdgeLen=Math.max(dp[i][j],maxEdgeLen);
                }
            }
        }
        return maxEdgeLen*maxEdgeLen;
    }
}

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