int stck[65535],sum[65535];
int largestRectangleArea(int* hgt, int hgtsz) {
    int top = 0,ret = 0;
    for(int i = 0; i <= hgtsz; i ++)
    {
        int now = (i == hgtsz) ? 0:hgt[i];
        while(top && now <= hgt[stck[top-1]])
        {
            int h = hgt[stck[--top]];
            int width = (top?i-1 - stck[top-1] : i);
            h =  h > width ? width: h;
            if(h > ret)
                ret  = h;
        }
        stck[top++] = i;
    }
    return ret*ret;
}
int maximalSquare(char** matrix, int row, int col) {
    int ret = 0,tmp;
    memset(sum,0,sizeof(int)*col);
    for(int r = 0; r < row; r++)
    {
        for(int c = 0; c < col; c++)
            sum[c] += (matrix[r][c]=='1'?1:-sum[c]);
        tmp = largestRectangleArea(sum,col);
        if(tmp > ret)
            ret = tmp;
    }
    return ret;
}