Submission #494893

#	Time	Username	Problem	Language	Result	Execution time	Memory
494893		jamezzz	Boat (APIO16_boat)	C++17	9 / 100	746 ms	8004 KiB

boat

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

#ifdef DEBUG
#define dbg(...) printf(__VA_ARGS__);
#define getchar_unlocked getchar
#else
#define dbg(...)
#endif
#define sf scanf
#define pf printf
#define fi first
#define se second
#define pb push_back
#define sz(x) (int)x.size()
#define mnto(x,y) x=min(x,(__typeof__(x))y)
#define mxto(x,y) x=max(x,(__typeof__(x))y)
#define INF 1023456789
#define LINF 1023456789123456789
#define all(x) x.begin(), x.end()
#define disc(x) sort(all(x));x.resize(unique(all(x))-x.begin());
typedef long long ll;
typedef long double ld;
typedef pair<int, int> ii;
typedef pair<ll, ll> pll;
typedef tuple<int, int, int> iii;
typedef tuple<int, int, int, int> iiii;
typedef vector<int> vi;
typedef vector<ii> vii;
typedef vector<pll> vll;
mt19937 rng(time(0));

#define mod 1000000007

inline int add(int a,int b){
	int r=a+b;
	while(r>=mod)r-=mod;
	while(r<0)r+=mod;
	return r;
}

inline int mult(int a,int b){
	return (int)(((ll)a*b)%mod);
}

inline int rd(){
    int x=0;
    char ch=getchar_unlocked();
    while(ch<'0'||ch>'9')ch=getchar_unlocked();
    while(ch>='0'&&ch<='9'){
		x=(x<<3)+(x<<1)+ch-'0';
		ch=getchar_unlocked();
	}
    return x;
}

int n,m,a[505],b[505],memo[505][1005],c[1005][505],c2[505][505],w[1005][505],inv[505];
vector<int> v[1005],d;

int fp(int a,int x){
	if(x==0)return 1;
	int t=fp(a,x/2);
	int r=mult(t,t);
	if(x%2)r=mult(r,a);
	return r;
}

int choose(int a,int b){
	int r=1;
	for(int i=a-b+1;i<=a;++i)r=mult(r,i);
	for(int i=1;i<=b;++i)r=mult(r,inv[i]);
	return r;
}

int dp(int i,int j){//covered up to the ith segment,now deciding for jth segment
	if(i==n)return 1;
	if(j==m)return (i!=0);
	if(memo[i][j]!=-1)return memo[i][j];
	int s=upper_bound(all(v[j]),i)-v[j].begin();
	int ans=dp(i,j+1);
	for(int t=s;t<sz(v[j]);++t){
		ans=add(ans,mult(w[j][t-s+1],dp(v[j][t],j+1)));
	}
	return memo[i][j]=ans;
}

int main(){
	sf("%d",&n);
	for(int i=1;i<=n;++i){
		sf("%d%d",&a[i],&b[i]);
		d.pb(a[i]);d.pb(b[i]+1);
	}
	disc(d);m=sz(d);d.pb(d.back()+1);
	for(int i=1;i<=n;++i){
		for(int j=0;j<m;++j){
			if(a[i]<=d[j]&&d[j]<=b[i])v[j].pb(i);
		}
	}
	for(int i=1;i<=n;++i)inv[i]=fp(i,mod-2);
	for(int i=0;i<m;++i){
		int a=d[i+1]-d[i];
		for(int b=1;b<=sz(v[i]);++b){
			c[i][b]=choose(a,b);
		}
	}
	for(int i=1;i<=n;++i){
		for(int j=0;j<=i;++j){
			c2[i][j]=choose(i,j);
		}
	}
	for(int i=0;i<m;++i){
		int a=d[i+1]-d[i];
		for(int b=1;b<=sz(v[i]);++b){
			for(int k=0;k<b;++k){
				w[i][b]=add(w[i][b],mult(c[i][k+1],c2[b][k]));
			}
		}
	}
	memset(memo,-1,sizeof memo);
	pf("%d\n",dp(0,0));
}

/*
2
1 2
2 3
*/

Compilation message (stderr)

boat.cpp: In function 'int main()':
boat.cpp:112:7: warning: unused variable 'a' [-Wunused-variable]
  112 |   int a=d[i+1]-d[i];
      |       ^
boat.cpp:88:4: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   88 |  sf("%d",&n);
      |    ^
boat.cpp:90:5: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   90 |   sf("%d%d",&a[i],&b[i]);
      |     ^

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