Submission #1011070

#	Time	Username	Problem	Language	Result	Execution time	Memory
1011070		medmdg	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	135 ms	10516 KiB

fancyfence

#include<bits/stdc++.h>
using namespace std;
#define int long long
#define all(v) v.begin(),v.end()
#define pb push_back
const int mod=1e9+7;
int f(int a){
    a%=mod;
    return ((a%mod*(a+1)%mod)%mod*500000004%mod)%mod;
}
const int mxn=1e5+100;
int sz[mxn];
int W[mxn];
int p[mxn];
int find(int node){
    return node==p[node]?node:p[node]=find(p[node]);
}
void merge(int a,int b){
    a=find(a);
    b=find(b);
    if(a==b) return;
    if(sz[a]<sz[b]) swap(a,b);
    sz[a]+=sz[b];
    p[b]=a;
    W[a]=(W[a]%mod+W[b]%mod)%mod;
}
signed main(){
    int n;
    cin>>n;
    vector<int> h(n+1);
    vector<int> w(n+1);
    for(int i=0;i<n;i++){
        cin>>h[i];
    }
    for(int i=0;i<n;i++){
        cin>>w[i];
    }
    int ans=0;
    for(int i=0;i<n;i++){
        ans=(ans%mod+f(h[i])%mod*f(w[i])%mod)%mod;
    }
    ans%=mod;
    vector<vector<int>> v;
    for(int i=0;i+1<n;i++){
        v.pb({i,i+1,min(h[i],h[i+1])});
    }
    sort(all(v),[&](auto a,auto b){
        return a[2]>b[2];
    });
    for(int i=0;i<n;i++){
        sz[i]=1;
        p[i]=i;
        W[i]+=w[i];
    }
    for(auto x:v){
        int a=W[find(x[0])];
        int b=W[find(x[1])];
        a+=mod;
        b+=mod;
        a%=mod;
        b%=mod;
        merge(x[0],x[1]);
        ans=(ans%mod+a%mod*b%mod*f(x[2])%mod)%mod;
    }
    cout<<ans<<endl;
}

• 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