Submission #885138

#	Time	Username	Problem	Language	Result	Execution time	Memory
885138		8pete8	Fancy Fence (CEOI20_fancyfence)	C++17	0 / 100	4 ms	4700 KiB

fancyfence

#include<iostream>
#include<stack>
#include<map>
#include<vector>
#include<string>
#include<unordered_map>
#include <queue>
#include<cstring>
#include<limits.h>
#include <cassert>
#include<cmath>
#include<set>
#include<algorithm>
#include <iomanip>
#include<numeric> //gcd(a,b)
#include<bitset>
using namespace std;
#define ll long long
#define f first
#define endl "\n"
#define s second
#define pii pair<int,int>
#define ppii pair<int,pii>
#define vi vector<int>
#define pb push_back
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
#define F(n) for(int i=0;i<n;i++)
#define lb lower_bound
#define ub upper_bound
#define fastio ios::sync_with_stdio(false);cin.tie(NULL);
#pragma GCC optimize ("03,unroll-loops")
using namespace std;
#define int long long
const int mod=1e9+7,mxn=1e5+5,lg=30,inf=1e18,minf=-1e18;
pii pos[mxn+10];
int ans=0,pa[mxn+10],add=0,sz[mxn+10],fac[mxn+10],inv=500000004;
int find(int u){return (pa[u]==u)?u:pa[u]=find(pa[u]);}
int cal(int w){
    return (((w*(w+1)%mod)*inv)%mod);
}
void merg(int a,int b){
    int c=b-a;
    a=find(a),b=find(b);
    pa[a]=b;
    add-=(cal(sz[b])+cal(sz[a]));
    add=(add+mod)%mod;
    sz[b]+=sz[a];
    sz[b]+=c;
    add+=cal(sz[b]);
    add%=mod;
}
int32_t main(){
    int n;cin>>n;
    vector<pii>v(n);
    for(int i=0;i<n;i++)cin>>v[i].f,v[i].s=i,pa[i]=i;
    for(int i=0;i<n;i++){
        int a;cin>>a;
        if(i)pos[i]={pos[i-1].s,pos[i-1].s+a};
        else pos[i]={1,a+1};
    }
    sort(rall(v));
    int cur=0,cnt=0;
    for(int i=0;i<n;i++){
        while(cur<n&&v[cur].f==v[i].f){
            merg(pos[v[cur].s].f,pos[v[cur].s].s);
            cur++;
        }
        int ch=v[i].f,nh=((cur>=n)?0:v[cur].f);
        int tmp=(((((((ch*(ch+1))%mod)*inv)%mod)-((((nh*(nh+1))%mod)*inv)%mod))+mod)%mod);
        ans=(ans+(add*tmp)%mod)%mod;
        i=cur-1;
    }
    cout<<ans;
}

Compilation message (stderr)

fancyfence.cpp: In function 'int32_t main()':
fancyfence.cpp:63:15: warning: unused variable 'cnt' [-Wunused-variable]
   63 |     int cur=0,cnt=0;
      |               ^~~

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