Submission #390431

#	Time	Username	Problem	Language	Result	Execution time	Memory
390431		BJoozz	Fancy Fence (CEOI20_fancyfence)	C++14	100 / 100	30 ms	5392 KiB

fancyfence

#include<bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define pb push_back
#define int long long
const int MAX=1e5+3,mod=1e9+7;
int dp[MAX];
void maxx(int &a,int b){if(b>a) a=b;}
void minn(int &a,int b){if(b<a) a=b;}
void PL(int &a,int b){a+=b;if(a>=mod) a-=mod;}
int b[MAX];
int a[MAX];
int D[MAX];
int gs(int x){
    return (x*(x+1)/2)%mod;
}
signed main(){
    ios::sync_with_stdio(0);cin.tie(0);
    int n;
    cin>>n;
    for(int i=1;i<=n;i++){
        cin>>a[i];
    }
    int ans=0;
    int top=0;
    for(int i=1,x;i<=n;i++){
        cin>>x;
        b[i]=(b[i-1]+x)%mod;
        while(a[i]<a[D[top]]) top--;
        int u=D[top];
        dp[i]=( gs(a[i])*(b[i]-b[u])+dp[u] )%mod;
        (ans+=dp[u]*x+gs(a[i])*(gs(x)+x*(b[i-1]-b[u])%mod) )%=mod;
        D[++top]=i;
    }
    PL(ans,mod);
    cout<<ans;
}

• 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