#define here cerr<<"===========================================\n"
#define dbg(x) cerr<<#x<<": "<<x<<endl;
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
#define ld double
#define ll long long
#define llinf 100000000000000000LL // 10^17
#define pb push_back
#define popb pop_back
#define fi first
#define sc second
#define endl '\n'
#define pll pair<ll,ll>
#define pld pair<ld,ld>
#define sz(a) (ll)(a.size())
#define all(a) a.begin(),a.end()
#define ceri(a,l,r) {cerr<<#a<<": ";for(ll i_ = l;i_<=r;i_++) cerr<<a[i_]<< " ";cerr<<endl;}
#define cer(a) {cerr<<#a<<": ";for(ll x_ : a) cerr<<x_<< " ";cerr<<endl;}
#define daj_mi_malo_vremena ios_base::sync_with_stdio(false);cerr.tie(0);cout.tie(0);cin.tie(0);
using namespace std;
using namespace __gnu_pbds;
#define mod 1000000007
ll add(ll x,ll y){
x+=y;
if(x<0){
x%=mod;
x+=mod;
}else{
if(x>=mod) x%=mod;
}
return x;
}
ll mul(ll a,ll b){
ll ans = (a*b)%mod;
if(ans<0) ans+=mod;
return ans;
}
ll po(ll x,ll y){
if(y==0) return 1LL;
ll ans = po(x,y/2);
ans = mul(ans,ans);
if(y&1) ans = mul(ans,x);
return ans;
}
ll inv(ll x){return po(x,mod-2);}
#define maxn 2005
ll n;
pll a[maxn];
pll seg[maxn];
ll dp[maxn][maxn];
map<pll,ll> ch;
ll cnt = 0;
bool in(pll x,pll y){
return x.fi>=y.fi&&x.sc<=y.sc;
}
ll calc(ll n,ll k){
if(ch.count({n,k})){
//cerr<<"nk: " <<n<<" "<<k<< " "<<ch[{n,k}]<<endl;
return ch[{n,k}];
}
ch[{n,n}] = 1;
ch[{n,0}] = 1;
ll ans = 1;
for(ll j = 1;j<min(n,2001LL);j++){
ans = mul(ans,n-j+1);
ans = mul(ans,inv(j));
ch[{n,j}] = ans;
}
//cerr<<"nk: " <<n<<" "<<k<< " "<<ch[{n,k}]<<endl;
return ch[{n,k}];
}
void tc(){
cin >> n;
set<ll> s;
for(ll i = 1;i<=n;i++){
cin >> a[i].fi >> a[i].sc;
s.insert(a[i].fi); s.insert(a[i].sc+1);
}
auto it = s.begin(); it++;
while(it!=s.end()){
auto it2 = it;
it2--;
seg[++cnt] = {(*it2),(*it)-1};
it++;
}
//here;
//for(ll i = 1;i<=cnt;i++) cerr<<seg[i].fi<<" "<<seg[i].sc<<endl;
//here;
dp[0][0] = 1;
for(ll i = 1;i<=cnt;i++) dp[0][i] = 1;
for(ll i = 1;i<=n;i++){
for(ll k = 1;k<=cnt;k++){
for(ll j = i;j>=1;j--){
if(!in(seg[k],a[j])) break;
dp[i][k] = add(dp[i][k],mul(dp[j-1][k-1],calc(seg[k].sc-seg[k].fi+1,i-j+1)));
if(j>=2) dp[i][k] = add(dp[i][k],mul(dp[j-2][k-1],calc(seg[k].sc-seg[k].fi+1,i-j+1)));
}
dp[i][k] = add(dp[i][k],dp[i][k-1]);
}
}
//for(ll i = 1;i<=n;i++) ceri(dp[i],1,cnt);
ll ans = dp[n][cnt];
if(n>1) ans = add(ans,dp[n-1][cnt]);
cout<<ans<<endl;
}
int main(){
daj_mi_malo_vremena
calc(5,4);
int t; t = 1;
while(t--){
tc();
}
return 0;
}
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
6 ms |
6228 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
6 ms |
6228 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
170 ms |
25640 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
| # |
결과 |
실행 시간 |
메모리 |
Grader output |
| 1 |
Incorrect |
6 ms |
6228 KB |
Output isn't correct |
| 2 |
Halted |
0 ms |
0 KB |
- |
