【悬线法】P1169 [ZJOI2007]棋盘制作

#include<iostream>
#include<algorithm>
#include<cstring>
using std::cin;
using std::cout;
using std::max;
using std::min;
using std::endl;

bool c[2010][2010];
int n, m;
int right[2010][2010], left[2010][2010], up[2010][2010];

int main()
{
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            cin>> c[i][j];

            left[i][j] = j;

            right[i][j] = j;

            up[i][j] = 1;
        }
    }
    for (int i = 1; i <= n; i++)
        for (int j = 2; j <= m; j++)
            if (c[i][j] != c[i][j - 1])
                left[i][j] = left[i][j - 1];
    for (int i = 1; i <= n; i++)
        for (int j = m - 1; j > 0; j--)
            if (c[i][j] != c[i][j + 1])
                right[i][j] = right[i][j + 1];
    int maxs1 = -0x3f3f3f3f;
    int maxs2 = -0x3f3f3f3f;
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= m; j++)
        {
            if (i > 1 && c[i][j] != c[i - 1][j])

            {
                left[i][j] = max(left[i][j], left[i - 1][j]);

                right[i][j] = min(right[i][j], right[i - 1][j]);

                up[i][j] = up[i - 1][j] + 1;
            }
            int a = right[i][j] - left[i][j] + 1;
            int b = min(a, up[i][j]);

            maxs1 = max(maxs1, b * b);

            maxs2 = max(maxs2, a * up[i][j]);

        }
    }
    cout << maxs1 << endl;
    cout << maxs2;
}