Submission #1159611

#	Time	Username	Problem	Language	Result	Execution time	Memory
1159611		tvgk	Tents (JOI18_tents)	C++20	100 / 100	142 ms	93836 KiB

tents

#include<bits/stdc++.h>
using namespace std;
#define task "a"
#define se second
#define fi first
#define ll long long
#define ii pair<ll, ll>
const long mxN = 3e3 + 7, MOD = 1e9 + 7;

ll gt[mxN], rev[mxN], f[mxN][mxN], sum[mxN][mxN];
int nRow, nCol;

ll pw(ll j, int mx)
{
    if (!mx)
        return 1;

    ll res = pw(j, mx / 2);
    res = res * res % MOD;
    if (mx % 2)
        return res * j % MOD;
    return res;
}

ll C(int u, int v)
{
    if (u > v)
        return 0;
    return gt[v] * rev[u] % MOD * rev[v - u] % MOD;
}

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    //freopen(task".INP", "r", stdin);
    //freopen(task".OUT", "w", stdout);

    cin >> nRow >> nCol;

    int mxn = max(nRow, nCol);
    gt[0] = rev[0] = 1;
    for (int i = 1; i <= mxn; i++)
    {
        gt[i] = gt[i - 1] * i % MOD;
        rev[i] = pw(gt[i], MOD - 2);
    }

    for (int i = 0; i <= mxn; i++)
    {
        sum[0][i] = f[0][i] = 1;
        for (int j = 1; j <= i; j++)
        {
            f[j][i] = f[j - 1][i] * C(2, i - j * 2 + 2) % MOD;
            sum[j][i] = sum[j - 1][i - 1] * i * 4 % MOD + sum[j - 1][i];
            sum[j][i] %= MOD;
        }
    }

    ll ans = 0;
    for (int i = 0; i <= nRow; i++)
    {
        for (int j = 0; j <= nCol; j++)
        {
            int Row = nRow - 2 * i - j;
            int Col = nCol - 2 * j - i;
            if (Row > Col)
                swap(Row, Col);
            if (Row < 0)
                break;

            ll inc = f[i][nRow] * f[j][nCol] % MOD * C(i, nCol - 2 * j) % MOD * C(j, nRow - 2 * i) % MOD;
            inc = inc * sum[Row][Col] % MOD;
            ans = (ans + inc) % MOD;
        }
    }
    cout << (ans + MOD - 1) % MOD;
}

• Subtask 1: 48 / 48
• Subtask 2: 52 / 52