Submission #3425501

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Source Code Expand

// g++ -std=c++11 a.cpp
#include<iostream>
#include<vector>
#include<string>
#include<algorithm>	
#include<map>
#include<set>
#include<unordered_map>
#include<utility>
#include<cmath>
#include<random>
#include<cstring>
#include<queue>
#include<stack>
#include<bitset>
#include<cstdio>
#include<sstream>
#include<iomanip>
#include<assert.h>
#include<typeinfo>
#define loop(i,a,b) for(int i=a;i<b;i++) 
#define rep(i,a) loop(i,0,a)
#define FOR(i,a) for(auto i:a)
#define pb push_back
#define all(in) in.begin(),in.end()
#define shosu(x) fixed<<setprecision(x)
#define show1d(v) rep(i,v.size())cout<<" "<<v[i];cout<<endl<<endl;
#define show2d(v) rep(i,v.size()){rep(j,v[i].size())cout<<" "<<v[i][j];cout<<endl;}cout<<endl;
using namespace std;
//kaewasuretyuui
typedef long long ll;
#define int ll
typedef int Def;
typedef pair<Def,Def> pii;
typedef vector<Def> vi;
typedef vector<vi> vvi;
typedef vector<pii> vp;
typedef vector<vp> vvp;
typedef vector<string> vs;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef pair<Def,pii> pip;
typedef vector<pip>vip;
//#define mt make_tuple
//typedef tuple<int,int,int> tp;
//typedef vector<tp> vt;
template<typename A,typename B>bool cmin(A &a,const B &b){return a>b?(a=b,true):false;}
template<typename A,typename B>bool cmax(A &a,const B &b){return a<b?(a=b,true):false;}
//template<class C>constexpr int size(const C &c){return (int)c.size();}
//template<class T,size_t N> constexpr int size(const T (&xs)[N])noexcept{return (int)N;}
const double PI=acos(-1);
const double EPS=1e-9;
Def inf = sizeof(Def) == sizeof(long long) ? 2e18 : 1e9+10;
int dx[]={0,1,0,-1};
int dy[]={1,0,-1,0};
//nCr mod m
#define MOD 1000000007
#define M 1000000
vector<ll> fact;
bool h=false;
void init(){
	h=true;
	fact=vector<ll>(M);
	fact[0]=fact[1]=1;
	loop(i,2,M)fact[i]=fact[i-1]*i%MOD;
}
// a^b mod MOD
ll powmod(ll a,ll b,ll m=MOD){
	ll out=1;
	ll p=a%m;
	while(b){
		if(b&1)out=out*p%m;
		p=p*p%m;
		b>>=1;
	}
	return out;
}
//nCr
ll nCr(ll n,ll r,ll m=MOD){
	if(!h)init();
	if(n<0||r<0||n<r)return 1;//??????
	ll out=fact[n]*powmod(fact[r]*fact[n-r]%m,m-2,m)%m;
	return out;
}
int n;
vi in;
pii f(int l,int r,int a){
	int mi=inf;
	loop(i,l,r)mi=min(mi,in[i]);
	
	vi t={l-1};
	loop(i,l,r)if(in[i]==mi)t.pb(i);
	t.pb(r);
	vp in;
	
	int w=r-l;
	rep(i,t.size()-1)if(t[i]+1-t[i+1])in.pb(f(t[i]+1,t[i+1],mi)),w-=t[i+1]-t[i]-1;
	
	int b=powmod(2,mi-a,MOD),c=powmod(2,w,MOD),d=(MOD+powmod(2,mi-a,MOD)-2)%MOD;
	rep(i,in.size()){
		(b*=in[i].first)%=MOD;
		(c*=in[i].first+in[i].second)%=MOD;
		(d*=in[i].first)%=MOD;
	}
	return {b,(c+d)%MOD};
}
signed main(){
	init();
	cin>>n;
	in=vi(n);
	rep(i,n)cin>>in[i];
	pii a=f(0,n,0);
	cout<<a.second<<endl;
}

Submission Info

Judge Result