Submission #1008123

#	Time	Username	Problem	Language	Result	Execution time	Memory
1008123		kebine	Fancy Fence (CEOI20_fancyfence)	C++17	12 / 100	5 ms	4996 KiB

fancyfence

#include <bits/stdc++.h>
using namespace std;
#define pii pair<ll,ll>
#define REP(i,x,y) for(ll i=x;i<=y;i++)
#define freeopen freopen("input.txt","r",stdin); freopen("output.txt","w",stdout);
#define mod 1000000007
#define pb push_back
#define mk make_pair
#define ll long long
#define foor(x,vec) for(auto x:vec ){cout<<x<<" ";}
#define fi first
#define se second
#define MAXN 700069
#define lld long double
#define cha ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ffl fflush(stdout)
#define sst string
#define pii pair<ll,ll>
ll mvx[]={0,0,-1,1};
ll mvy[]={1,-1,0,0};
ll n,q;
ll a,b;
ll h[MAXN],w[MAXN];
ll ps[MAXN];
ll dp[MAXN];
ll idx[MAXN];
ll mul(ll a,ll b){
    a=a%mod;
    b=b%mod;
    a*=b;
    a%=mod;
    return a;
}

int main(){
    cin>>n;
    REP(i,1,n)cin>>h[i];
    REP(i,1,n)cin>>w[i];
    REP(i,1,n){
        ps[i]=ps[i-1]+w[i];
    }
    stack <ll> stck;
    stck.push(0);
    REP(i,1,n){
        while(stck.size() && h[i]<h[stck.top()]){
            stck.pop();
        }
        idx[i]=stck.top();
        stck.push(i);
    }
    ll ans=0;
    REP(i,1,n){
        ll val=(dp[idx[i]])%mod*(w[i]);
        val%=mod;
        val=val+mul(h[i]*(h[i]+1)/2,w[i]*(w[i]+1)/2)%mod;
        val%=mod;
        val=val+mul(mul(h[i],h[i]+1)/2,(ps[i-1]-ps[idx[i]]))%mod;
        ans+=val;
        ans%=mod;
        dp[i]=dp[idx[i]]+mul(mul(h[i],h[i]+1)/2,(ps[i]-ps[idx[i]]));
        dp[i]%=mod;
    }
    cout<<ans<<endl;
}

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