Submission #557920

#	Time	Username	Problem	Language	Result	Execution time	Memory
557920		DJ035	Fancy Fence (CEOI20_fancyfence)	C++17	100 / 100	104 ms	5352 KiB

fancyfence

#include <bits/stdc++.h>
#define MEM 111111
#define sanic ios_base::sync_with_stdio(0)
#define x first
#define y second
#define pf push_front
#define pb push_back
#define all(v) v.begin(), v.end()
#define sz size()
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pi;
const ll INF = 1e13+7;
const ll MOD = 1e9+7;
ll gcd(ll a, ll b){
    if(a%b) return gcd(b, a%b);
    return b;
}
ll c2(ll n){
    ll ret = n*(n-1)/2LL;
    ret %= MOD;
    ret += MOD;
    ret %= MOD;
    return ret;
}
ll hp(ll l, ll r){
    ll a=c2(l+1);
    ll b=c2(r+1);
    return ((b-a)%MOD+MOD)%MOD;
}
ll n,m,t,c;
ll h[MEM], w[MEM];
signed main(){
    //sanic; cin.tie(0); cout.tie(0);
    cin >> n;
    for(int i=0; i<n; i++)
        cin >> h[i];
    for(int i=0; i<n; i++)
        cin >> w[i];
    stack<pi> s;
    ll ans=0;
    for(int i=0; i<n; i++){
        if(s.empty()){
            s.push({h[i], w[i]});
            continue;
        }
        ll p=0;
        while(s.top().x>h[i]){
            ll h1=s.top().x, w1=s.top().y;
            s.pop();
            ans = (ans+(hp(max((s.empty() ? h[i]:s.top().x), h[i]), h1)*c2(w1+1))%MOD+MOD)%MOD;
            p = w1;
            //cout << h1 << ' ' << w1 << '\n';
            if(s.empty() || s.top().x<h[i]) break;
            pi ff=s.top();
            s.pop();
            ff.y += w1;
            ff.y %= MOD;
            ff.y += MOD;
            ff.y %= MOD;
            s.push(ff);
        }
        //cout << ans << '\n';
        if(!s.empty() && s.top().x==h[i]) {
            pi ff=s.top();
            s.pop();
            ff.y += w[i];
            ff.y %= MOD;
            ff.y += MOD;
            ff.y %= MOD;
            s.push(ff);
        }
        else s.push({h[i], ((w[i]+p)%MOD+MOD)%MOD});
        /*
        stack<pi> gg=s;
        while(!gg.empty()){
            cout << gg.top().x << ' ' << gg.top().y << '\n';
            gg.pop();
        }*/
    }
    while(!s.empty()){
        ll h1=s.top().x, w1=s.top().y;
        s.pop();
        ans = (ans+(hp((s.empty()?0:s.top().x), h1)*c2(w1+1))%MOD+MOD)%MOD;
        //cout << h1 << ' ' << w1 << '\n';
        if(s.empty()) break;
        pi ff=s.top();
        s.pop();
        ff.y += w1;
        ff.y %= MOD;
        ff.y += MOD;
        ff.y %= MOD;
        s.push(ff);
    }
    cout << ans;
}
/*
10
1 3 2 4 2 1 3 5 6 7
2 3 5 4 6 2 3 5 6 7
3
2 3 1
3 1 2
5
2 3 3 4 1
2 4 5 1 2
660
*/

• 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