[leedcode 85] Maximal Rectangle

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

public class Solution {
    public int maximalRectangle(char[][] matrix) {
        //利用上题的思路，先求出每一列的连续1个数，保存在DP二维数组中，然后对每一行进行findRectangle
        if(matrix.length<1) return 0;
        int row=matrix.length;
        int col=matrix[0].length;
        int dp[][]=new int[row][col];
        int res=0;
        for(int i=0;i<row;i++){
            for(int j=0;j<col;j++){
                if(i==0){
                    dp[i][j]=matrix[i][j]-'0';
                }else{
                    if(matrix[i][j]=='1')
                      dp[i][j]=dp[i-1][j]+1;
                }
            }
        }
        for(int i=0;i<row;i++){
            int temp= findRectangle(dp[i]);
            res=Math.max(temp,res);
        }
         return res;
        
    }
    public int findRectangle(int [] height){
        Stack<Integer> stack=new Stack<Integer>();
        height=Arrays.copyOf(height,height.length+1);
        //if(height.length==0) return 0;
        //if(height.length==1) return height[0];
        height[height.length-1]=0;
        int res=0;
        int i=0;
        while(i<height.length){
            if(stack.empty()||height[i]>=height[stack.peek()])stack.push(i++);
            else{
                int temp=stack.pop();
                res=Math.max(res,height[temp]*(stack.empty()?i:(i-stack.peek()-1)));
            }
        }
        return res;
    }
}