Submission #792984

#	Time	Username	Problem	Language	Result	Execution time	Memory
792984		algorithm16	Boat (APIO16_boat)	C++14	27 / 100	1237 ms	524288 KiB

boat

#include<iostream>
#include<cstring>
#include<vector>
#include<algorithm>
using namespace std;
int n,dp[1505][505][505],a[505],b[505],inv[505],mod=1e9+7;
vector <int> v;
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 rec(int idx,int x,int cnt) {
	if(idx>=v.size()-1) return 0;
	if(x>=n) return 1;
	if(dp[idx][x][cnt]!=-1) return dp[idx][x][cnt];
	int ret=0;
	ret=sum(ret,rec(idx,x+1,cnt)); // 0
	
	//if(idx==0 && x==1 && cnt==1) cout << ret << "\n";
	if(v[idx]>=a[x] && v[idx+1]-1<=b[x]) {
		if(cnt<=v[idx+1]-1-v[idx]) ret=sum(ret,mul(rec(idx,x+1,cnt+1),mul(v[idx+1]-v[idx]-cnt,inv[cnt+1])));
	}
	for(int i=idx+1;i<v.size()-1;i++) {
		if(v[i]>=a[x] && v[i+1]-1<=b[x]) ret=sum(ret,mul(rec(i,x+1,1),v[i+1]-v[i]));
	}
	dp[idx][x][cnt]=ret;
	//cout << idx << " " << x << " " << cnt << " " << ret << "\n";
	return ret;
}
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=0;i<v.size()-1;i++) {
		for(int j=0;j<n;j++) {
			for(int k=0;k<=j;k++) {
				dp[i][j][k]=-1;
			}
		}
	}
	for(int i=1;i<=n;i++) {
		inv[i]=exp(i,mod-2);
	}
	cout << rec(0,0,0)-1;
	return 0;
}

Compilation message (stderr)

boat.cpp: In function 'int rec(int, int, int)':
boat.cpp:21:8: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 |  if(idx>=v.size()-1) return 0;
      |     ~~~^~~~~~~~~~~~
boat.cpp:31:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |  for(int i=idx+1;i<v.size()-1;i++) {
      |                  ~^~~~~~~~~~~
boat.cpp: In function 'int main()':
boat.cpp:58:15: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   58 |  for(int i=0;i<v.size()-1;i++) {
      |              ~^~~~~~~~~~~

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