Submission #632102

#	Time	Username	Problem	Language	Result	Execution time	Memory
632102		CSQ31	Boat (APIO16_boat)	C++17	100 / 100	1145 ms	4300 KiB

boat

#pragma GCC optimize("Ofast") 
#include <bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define sz(a) a.size()
#define all(a) a.begin(),a.end()
#define lb lower_bound
#define ub upper_bound
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
#define INF (int)(1e9)
#define debug(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false);\
debug("%s time : %.4fs\n", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
typedef long long int ll;
typedef long double ld;
typedef pair<ll,ll> PII;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
typedef vector<vector<ll>> VII;
ll gcd(ll a,ll b){if(!b)return a;else return gcd(b,a%b);}
const int MOD = 1e9+7;
int dp1[1001][501],dp2[1001][501]; //boat,group,cnt
int a[501],b[501],fac[501];
int binpow(int n,int k){
	int res = 1;
	while(k){
		if(k&1)res = res*1LL*n%MOD;
		n = n*1LL*n%MOD;
		k/=2;
	}
	return res;
}
int main()
{
	owo
	int n;
	cin>>n;
	fac[1] = 1;
	for(int i=2;i<=n;i++)fac[i] = fac[i-1]*1LL*i%MOD;
	for(int i=1;i<=n;i++)fac[i] = binpow(fac[i],MOD-2);
	vector<int>c;
	for(int i=0;i<n;i++){
		cin>>a[i]>>b[i];
		c.pb(a[i]);
		c.pb(b[i]+1);
	}
	sort(all(c));
	c.resize(unique(all(c)) - c.begin());
	int m = sz(c),tot = 1;
	for(int i=0;i<n;i++){
		tot = 1;
		for(int j=0;j+1<m;j++){
			int s = c[j+1]-c[j];
			for(int k=1;k<=min(n,s);k++)dp2[j][k] = dp1[j][k];
			if(a[i] <= c[j] && c[j] <= b[i]){ 
				//add you in new group
				dp2[j][1] += tot * 1LL * s%MOD;
				if(dp2[j][1]>=MOD)dp2[j][1]-=MOD;
				//add you to existing group
					for(int k=2;k<=min(n,s);k++){
						dp2[j][k] += dp1[j][k-1] * 1LL * (s-k+1)%MOD;
						if(dp2[j][k]>=MOD)dp2[j][k]-=MOD;
					}
			}
			for(int k=1;k<=min(n,s);k++){//update tot
				tot+=dp1[j][k] * 1LL * fac[k]%MOD;
				if(tot>=MOD)tot-=MOD;
			}	
		}
		for(int j=0;j+1<m;j++){
			int s = c[j+1]-c[j];
			for(int k=1;k<=min(n,s);k++){
				dp1[j][k] = dp2[j][k];
				dp2[j][k] = 0;
			}
			
		}
	}
	int ans = 0;
	for(int i=0;i<m;i++){
		for(int j=1;j<=n;j++){
			ans+=dp1[i][j]*1LL*fac[j]%MOD;
			ans%=MOD;
		}
	}
	cout<<ans;
}

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