LeetCode Maximal Square

Description

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 0
1 0 1 1 1
1 1 1 1 1
1 0 0 1 0

Return 4.

The original problem is here.

The original code is here.

My Solution

I solve this problem in C++, as below:

/*
*Maximal Square
*Author: shuaijiang
*Email: zhaoshuaijiang8@gmail.com
*/
#include<iostream>
#include<vector>
#include<stdlib.h>
using namespace std;

class Solution {
public:
    int maximalSquare(vector<vector<char>>& matrix) {
        int rowNum = matrix.size();
        if(rowNum <= 0)
            return 0;
        int colNum = matrix[0].size();
        vector<int> oneRow(colNum, 0);
        vector<vector<int>> dp;
        for(int i=0;i<rowNum;i++)
            dp.push_back(oneRow);
        int sideLength = 0;
        // get the maximum side length
        for(int i=0;i<rowNum;i++){
            for(int j=0;j<colNum;j++){
                dp[i][j] = matrix[i][j] - '0';
                if(i-1=>0 && j-1=>0 && dp[i][j]>0){
                    dp[i][j] = min(dp[i-1][j-1], min(dp[i-1][j], dp[i][j-1])) + 1;
                }
                if(dp[i][j] > sideLength)
                    sideLength = dp[i][j];
            }
        }
        return sideLength * sideLength;
    }
};

Note

To solve the problem, I use dynamic program and save the maximal side length of the square.