Submission #793031

#	Time	Username	Problem	Language	Result	Execution time	Memory
793031		algorithm16	Boat (APIO16_boat)	C++14	58 / 100	2079 ms	15128 KiB

boat

#include<iostream>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
int n,a[505],b[505],dp[1505][2][505][2],inv[505],m[1505][505],mod=1e9+7;
vector <int> v,v1;
vector <vector<int> > v2;
int sum(int a,int b) {
	return (a+b)%mod;
}
int mul(int a,int b) {
	return ((long long)a*b)%mod;
}
int exp(int a,int b) {
	if(!b) return 1;
	int ret=exp(a,b/2);
	if(b%2==0) return mul(ret,ret);
	return mul(mul(ret,ret),a);
}
int main()
{
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	for(int i=0;i<n;i++) {
		cin >> a[i] >> b[i];
		v.push_back(a[i]);
		v.push_back(b[i]);
		v.push_back(b[i]+1);
	}
	sort(v.begin(),v.end());
	v.erase(unique(v.begin(),v.end()),v.end());
	/*for(int i=0;i<v.size()-1;i++) {
		cout << v[i] << " " << v[i+1]-1 << "\n";
	}*/
	/*for(int i=0;i<n;i++) {
		a[i]=lower_bound(v.begin(),v.end(),a[i])-v.begin();
		b[i]=lower_bound(v.begin(),v.end(),b[i])-v.begin();
	}*/
	for(int i=1;i<=n;i++) {
		inv[i]=exp(i,mod-2);
	}
	for(int i=0;i<v.size()-1;i++) {
		for(int j=0;j<=n;j++) {
			dp[i][n%2][j][0]=1;
			dp[i][n%2][j][1]=1;
		}
	}
	for(int i=0;i<v.size()-1;i++) {
		for(int j=0;j<n;j++) {
			m[i][j]=mul(v[i+1]-v[i]-j,inv[j+1]);
		}
	}
	for(int x=n-1;x>=0;x--) {
		for(int idx=v.size()-2;idx>=0;idx--) {
			for(int cnt=0;cnt<=x;cnt++) {
				for(int a1=0;a1<2;a1++) {
					int ret=0;
					if(!a1) ret=sum(ret,dp[idx][(x+1)%2][cnt][0]); // 0
					if(v[idx+1]-1<=b[x]) {
						if(v[idx]>=a[x] && v[idx+1]-1<=b[x]) {
							if(cnt<=v[idx+1]-1-v[idx]) ret=sum(ret,mul(dp[idx][(x+1)%2][cnt+1][0],m[idx][cnt]));
						}
						ret=sum(ret,dp[idx+1][x%2][0][1]);
					}
					dp[idx][x%2][cnt][a1]=ret;
					//cout << idx << " " << x << " " << cnt << " " << a1 << "  " << ret << "\n";
				}
			}
		}
	}
	cout << dp[0][0][0][0]-1;
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:44:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   44 |  for(int i=0;i<v.size()-1;i++) {
      |              ~^~~~~~~~~~~
boat.cpp:50:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   50 |  for(int i=0;i<v.size()-1;i++) {
      |              ~^~~~~~~~~~~

• Subtask 1: 9 / 9
• Subtask 2: 22 / 22
• Subtask 3: 27 / 27
• Subtask 4: 0 / 42