Submission #1112352

#	Time	Username	Problem	Language	Result	Execution time	Memory
1112352		squatrian	Fancy Fence (CEOI20_fancyfence)	C++17	0 / 100	2 ms	592 KiB

fancyfence

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
using std::mt19937_64;
using std::random_device;
using std::uniform_int_distribution;
#include <numeric>
#define ff              first
#define ss              second
#define int             long long
#define pb              push_back
#define mp              make_pair
#define pii             pair<int,int>
#define vi              vector<int>
#define mii             map<int,int>
#define pqb             priority_queue<int>
#define pqs             priority_queue<int,vi,greater<int> >
#define setbits(x)      __builtin_popcountll(x)
#define zrobits(x)      __builtin_ctzll(x)
#define mod             1000000007
#define inf             1e18
#define ps(x,y)         fixed<<setprecision(y)<<x
#define mk(arr,n,type)  type *arr=new type[n];
#define w(x)            int x; cin>>x; while(x--)
mt19937                 rng(chrono::steady_clock::now().time_since_epoch().count());
 
typedef tree<int, null_type, less<int>, rb_tree_tag, tree_order_statistics_node_update> pbds;
 
 
void c_p_c()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
// #ifndef ONLINE_JUDGE
//     freopen("art2.in", "r", stdin);
//     freopen("art2.out", "w", stdout);
// #endif
}
int dx[] = {1, -1, 0, 0};
int dy[] = {0, 0, 1, -1};
int exp(int x, int n, int m) {
    if(x == 0 and n == 0) return 1;
    x %= m; 
    int res = 1;
    while (n > 0) {
        if (n % 2 == 1) { res = res * x % m; }
        x = x * x % m;
        n /= 2;
    }
    return res;
}
int modinv(int n) {
    int r = 1;
    int p = mod - 2;
    while (p > 0) {
        if (p % 2 == 1) {
            r = (r * n) % mod;
        }
        n = (n * n) % mod;
        p /= 2;
    }
    return r;
}
signed main()
{   
   int t=1;
   c_p_c();
   // cin >> t;
   while(t--){
    int n;
    cin >> n;
    vector<int> a(n);
    vector<int> wei(n+1,0);
    for(int i = 0 ; i < n; i++){
        cin >> a[i];
    }
    for(int i = 1; i <= n; i++){
        cin >> wei[i];
        wei[i] += wei[i-1];
    }
    stack<pair<int,int>> s;
     s.push({0,0});
     vector<int> v(n);
     // cout<<1<<endl;
     for(int i = 1; i <= n; i++){
        while(!s.empty() and s.top().ff >= a[i-1]){
            s.pop();
        }
        v[i-1] = s.top().ss;
        s.push({a[i-1],i});
     }
     // cout<<1<<endl;
     while(!s.empty()){
        s.pop();
     }
     s.push({0,0});
     reverse(a.begin(),a.end());
     vector<int> b(n);
     for(int i = 1; i <= n; i++){
        while(!s.empty() and s.top().ff >= a[i-1]){
            s.pop();
        }
        b[i-1] = n-s.top().ss;
        s.push({a[i-1],i});
     }
     reverse(b.begin(),b.end());
     reverse(a.begin(),a.end());
     int ans = 0;
     set<pair<pair<int,int>,int>> st;
     for(int i = 0 ; i < n; i++){
        st.insert({{v[i],b[i]},a[i]});
        // cout<<v[i]<<" "<<b[i]<<endl;
     }
     vector<int> pref(n+2);
     for(auto &x:st){
       pref[x.ff.ff] += x.ss;
       pref[x.ff.ss] -= x.ss;
     }
     for(int i = 1 ; i <= n; i++){
        pref[i] += pref[i-1];
     }
     // for(int i = 0 ; i <= n; i++){
     //    cout<<pref[i]<<" ";
     // }
     // cout<<endl;
     set<pair<int,int>> se;
     for(int i = 0 ; i < n; i++){
        // int cur = 
        if(se.empty() or se.find({v[i],b[i]}) == se.end()){
          int cur_h = a[i];
          int cur_w = wei[b[i]]-wei[v[i]];
          int cur_rec = (((cur_h%mod)*(cur_h+1)%mod)%mod*modinv(2))%mod;
          int cur_rec2 = (((cur_w%mod)*(cur_w+1)%mod)%mod*modinv(2))%mod;
          int pref_h = pref[i] - a[i];
          int x = ((cur_rec*cur_rec2)%mod-(pref_h*cur_rec2)%mod+mod)%mod;
          // cout<<cur_h<<" "<<cur_w<<" "<<cur_rec<<" "<<cur_rec2<<" "<<x<<endl;
          ans = (ans+x)%mod;
          se.insert({v[i],b[i]});
        }
     }
     cout<<ans<<endl;


 
   }
    return 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