答案

public class Solution {
    char [][]matrix;
    int ROW;
    int COL;
    public static class Node
    {
        int row;

        int col;

        Node(int row, int col)
        {
            this.row = row;
            this.col = col;
        }
    }
    public boolean canAddRow(int row,int col,Node node)
    {
        if(node.row==ROW-1)
        {
            return false;
        }
        for(;col<=node.col;col++)
        {
            if(matrix[node.row+1][col]=='0')
            {
                return false;
            }
        }
        return true;
    }
    public boolean canAddCol(int row,int col,Node node)
    {
        if(node.col==COL-1)
        {
            return false;
        }
        for(;row<=node.row;row++)
        {
            if(matrix[row][node.col+1]=='0')
            {
                return false;
            }
        }
        return true;
    }
    public boolean isAllOne(int startRow,int endRow,int startCol,int endCol)
    {
        for(int row=startRow;row<=endRow;row++)
        {
            for(int col=startCol;col<=endCol;col++)
            {
                if(matrix[row][col]!='1')
                {
                    return false;
                }
            }
        }
        return true;
    }
    public int maximalRectangle(char[][] matrix)
    {
        if (matrix == null || matrix.length == 0 || matrix[0].length == 0)
        {
            return 0;
        }
        ROW = matrix.length;
        COL = matrix[0].length;
        this.matrix=matrix;
        int area = 0;
        Node[][] square = new Node[ROW][COL];
        for (int row = 0; row < ROW; row++ )
        {
            for (int col = 0; col < COL; col++ )
            {
                square[row][col] = new Node(row, col);
            }
        }
        for (int row = 0; row < ROW; row++ )
        {
            for (int col = 0; col < COL; col++ )
            {
                if (matrix[row][col] == '1')
                {
                    if (row > 0)
                    {
                        square[row][col].row = Math.max(square[row][col].row,
                            square[row - 1][col].row);
                        square[row][col].col = Math.max(square[row][col].col,
                            square[row - 1][col].col-1);
                    }
                    if (col > 0)
                    {
                        square[row][col].row = Math.max(square[row][col].row,
                            square[row][col - 1].row-1);
                        square[row][col].col = Math.max(square[row][col].col,
                            square[row][col - 1].col);
                        if (row > 0)
                        {
                            square[row][col].row = Math.max(square[row][col].row,
                                square[row - 1][col - 1].row);
                            square[row][col].col = Math.max(square[row][col].col,
                                square[row - 1][col - 1].col);
                        }
                    }
                    while(canAddRow(row,col,square[row][col])&&canAddCol(row,col,square[row][col])
                        &&(matrix[square[row][col].row+1][square[row][col].col+1]=='1'))
                    {
                        square[row][col].row++;
                        square[row][col].col++;
                    }
                    //System.out.println(row+"\t"+col+":"+square[row][col].row+"\t"+square[row][col].col);
                }
            }
        }
        for (int row = 0; row < ROW; row++ )
        {
            for (int col = 0; col < COL; col++ )
            {
                if (matrix[row][col] == '1')
                {
                    int minRow=row;
                    int maxRow=square[row][col].row;
                    for(;minRow>0;minRow--)
                    {
                        if(!isAllOne(minRow-1,minRow-1,col,square[row][col].col))
                        {
                            break;
                        }
                    }
                    for(;maxRow<ROW-1;maxRow++)
                    {
                        if(!isAllOne(maxRow+1,maxRow+1,col,square[row][col].col))
                        {
                            break;
                        }
                    }
                    int minCol=col;
                    int maxCol=square[row][col].col;
                    for(;minCol>0;minCol--)
                    {
                        if(!isAllOne(row,square[row][col].row,minCol-1,col))
                        {
                            break;
                        }
                    }
                    for(;maxCol<COL-1;maxCol++)
                    {
                        if(!isAllOne(row,square[row][col].row,col,maxCol+1))
                        {
                            break;
                        }
                    }
                    
                    area=Math.max(area, (maxRow-minRow+1)*(square[row][col].col-col+1));
                    area=Math.max(area, (square[row][col].row-row+1)*(maxCol-minCol+1));
                }
            }
        }
        return area;
    }
}