Submission #528307

#	Time	Username	Problem	Language	Result	Execution time	Memory
528307		Deepesson	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	83 ms	3864 KiB

fancyfence

#include <bits/stdc++.h>
using ll = long long;
const ll MOD = 1e9+7;
typedef std::pair<ll,ll> pii;
ll gaussian(ll x){
    return ((x*(x+1LL))/2LL)%MOD;
}
ll get_local(pii u){
    return (gaussian(u.first)*gaussian(u.second))%MOD;
}
ll get_total(pii u){
    return (gaussian(u.first)*u.second)%MOD;
}
int main()
{
    ll ans=0;
    ll temp=0;
    int N;std::cin>>N;
    long long a[N],b[N];
    for(auto&x:a)std::cin>>x;
    for(auto&x:b)std::cin>>x;
    std::deque<pii> stack;
    for(int i=0;i!=N;++i){
        ll alpha=a[i],beta=b[i];
        pii local = {alpha,beta};
        ans=(ans+get_local(local))%MOD;
        ll k=0;
        while(stack.size()){
            auto __ = stack.back();
            if(__.first>=alpha){
                k=(k+stack.back().second)%MOD;
                temp-=get_total(stack.back());
                if(temp<0)temp+=MOD;
                local.second=(local.second+stack.back().second)%MOD;
                stack.pop_back();
            }else break;
        }
        ans=(ans+(((k*b[i])%MOD)*gaussian(alpha)))%MOD;
        ans=((((temp*b[i])+ans)%MOD))%MOD;
        stack.push_back(local);
        temp=(temp+get_total(local))%MOD;
    }
    std::cout<<ans<<"\n";
}

• Subtask 1: 0 / 0
• Subtask 2: 12 / 12
• Subtask 3: 13 / 13
• Subtask 4: 15 / 15
• Subtask 5: 15 / 15
• Subtask 6: 18 / 18
• Subtask 7: 27 / 27