Submission #758709

#	Time	Username	Problem	Language	Result	Execution time	Memory
758709		Trisanu_Das	Boat (APIO16_boat)	C++17	100 / 100	657 ms	4404 KiB

boat

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int mod=1e9+7;
int dp[1005][505], inv[505], a[505], b[505], c[1005];
set<int> s;
int f(int x, int y)
{
    if (!y)
        return 1;
    int res=f(x, y/2);
    if (y&1)
        return res*res%mod*x%mod;
    else
        return res*res%mod;
}
signed main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int n, m=0;
    cin >> n;
    for (int i=1; i<=n; i++)
        inv[i]=f(i, mod-2);
    for (int i=1; i<=n; i++)
    {
        cin >> a[i] >> b[i];
        s.insert(a[i]);
        s.insert(b[i]+1);
    }
    for (auto itr=s.begin(); itr!=s.end(); itr++)
        c[++m]=(*itr);
    for (int i=0; i<=n; i++)
        dp[0][i]=1;
    for (int i=1; i<m; i++)
    {
        for (int j=0; j<=n; j++)
        {
            dp[i][j]=dp[i-1][j];
            int num=1, cnt=0;
            for (int k=1; k<=j; k++)
            {
                if (a[j-k+1]<=c[i] && c[i+1]-1<=b[j-k+1])
                {
                    cnt++;
                    num=num*(c[i+1]-c[i]+cnt-1)%mod*inv[cnt]%mod;
                    dp[i][j]=(dp[i][j]+dp[i-1][j-k]*num)%mod;
                }
            }
        }
    }
    cout << dp[m-1][n]-1;
    return 0;
}

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 42 / 42