Submission #558160

#	Time	Username	Problem	Language	Result	Execution time	Memory
558160		Sweezy	Boat (APIO16_boat)	C++17	100 / 100	366 ms	8268 KiB

boat

#include <bits/stdc++.h>
using namespace std;

#define ll long long

const int mxN=500, M=1e9+7;
int n, a[mxN], b[mxN];
ll dp[mxN+1][2*mxN], c[2*mxN][mxN+1];
vector<int> pts;

inline ll modI(ll a, ll m) {
    return a<=1?a:(1-modI(m%a, a)*m)/a+m;
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    
    cin >> n;
    for(int i=0; i<n; ++i) {
        cin >> a[i] >> b[i], --a[i];
        pts.push_back(a[i]);
        pts.push_back(b[i]);
    }
    sort(pts.begin(), pts.end());
    pts.resize(unique(pts.begin(), pts.end())-pts.begin());
    for(int i=1; i<pts.size(); ++i) {
        c[i][1]=pts[i]-pts[i-1];
        for(int j=2; j<=n; ++j)
            c[i][j]=c[i][j-1]*(pts[i]-pts[i-1]+j-1)%M*modI(j, M)%M;
    }
    for(int i=0; i<pts.size(); ++i)
        dp[0][i]=1;
    for(int i=1; i<=n; ++i) {
        dp[i][0]=1;
        for(int j=1; j<pts.size(); ++j) {
            dp[i][j]=dp[i][j-1];
            for(int k=i, n2=0; k; --k) {
                if(pts[j]>a[k-1]&&pts[j]<=b[k-1]) {
                    ++n2;
                    dp[i][j]+=dp[k-1][j-1]*c[j][n2]%M;
                }
            }
            dp[i][j]%=M;
        }
    }
    cout << dp[n][pts.size()-1]-1;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:27:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   27 |     for(int i=1; i<pts.size(); ++i) {
      |                  ~^~~~~~~~~~~
boat.cpp:32:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   32 |     for(int i=0; i<pts.size(); ++i)
      |                  ~^~~~~~~~~~~
boat.cpp:36:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   36 |         for(int j=1; j<pts.size(); ++j) {
      |                      ~^~~~~~~~~~~

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