Submission #753898

#	Time	Username	Problem	Language	Result	Execution time	Memory
753898		epicci23	Fancy Fence (CEOI20_fancyfence)	C++17	0 / 100	1 ms	388 KiB

fancyfence

#include "bits/stdc++.h"
#pragma optimize ("Bismillahirrahmanirrahim")
using namespace std;
#define pb push_back
#define ff first
#define ss second
#define endl "\n" 
#define int long long
#define double long double
#define sz(x) ((int)(x).size())
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define what_is(x) cerr << #x << " is " << x << endl;
//#define m (l+r)/2
constexpr int N=200005;
constexpr int MOD=1000000007;
constexpr int  INF2 = LLONG_MAX;
constexpr int INF=(int)1e18;
constexpr int LOG=30;
typedef pair<int,int> pii;
typedef tuple<int,int,int> tp;
typedef priority_queue<pii,vector<pii>,greater<pii>> min_pq;
typedef priority_queue<pii> max_pq;
typedef long long ll;
//to think//
/*
 * graph approach
 * dp
 * dividing the problem to smaller statements
 * finding the real constraint
 * sqrt decomposition
 * greedy approach
 * pigeonhole principle
 * rewriting the problem/equality 
 * bitwise approaches
 * binary search if monotonic
 * divide and conquer
 * combinatorics
 * inclusion - exclusion
 * think like bfs
*/



inline int in()
{
  int x;cin >> x;
  return x;
}

inline string in2()
{
  string x;cin >> x;
  return x;
}

int add(int a,int b)
{
  if(a+b>=MOD) return a+b-MOD;
  return a+b;
}

int mult(int a,int b)
{
  if(a*b>=MOD) return (a*b)%MOD;
  return a*b;
}

int eks(int a,int b)
{
  if(a<b) return a-b+MOD;
  return a-b;
}

int fast(int a,int b)
{
  if(b==0) return 1;
  int res=fast(a,b/2);
  res=mult(res,res);
  if(b&1) res=mult(res,a);
  return res;
}

void solve()
{
  int n=in(),ans=0;
  array<int,2> ar[n+1];
  ar[0]=ar[n+1]={0,0};
  for(int i=1;i<=n;i++) ar[i][0]=in();
  for(int i=1;i<=n;i++) ar[i][1]=in();
  
  int pre[n+1];
  pre[0]=0;
  int xd=fast(2,MOD-2);
  auto get=[&](int a){
    return mult(xd,mult(a,eks(a,1LL)));
  };

  for(int i=1;i<=n;i++) pre[i]=add(pre[i-1],ar[i][1]);

  array<int,2> hist[n+1];
  stack<int> s;
  for(int i=1;i<=n;i++)
  {
    while(!s.empty() && ar[s.top()][0]>=ar[i][0]) s.pop();
    hist[i][0]=s.empty() ? 0 : s.top();
    s.push(i);
  }

  while(!s.empty()) s.pop();
  
  for(int i=n;i>=1;i--)
  {
    while(!s.empty() && ar[s.top()][0]>=ar[i][0]) s.pop();
    hist[i][1]=s.empty() ? n+1 : s.top();
    s.push(i);
  }

  while(!s.empty()) s.pop();

  map<pii,bool> mp;

  for(int i=1;i<=n;i++)
  {
    if(mp[{ar[i][0],hist[i][0]}]) continue;
    mp[{ar[i][0],hist[i][0]}]=1;
    int r=hist[i][1];
    int l=hist[i][0];
    int maxi=max(ar[l][0],ar[r][0]);
    int uz=add(1LL,eks(pre[r-1],pre[l]));
    //cout << maxi << endl;
    ans=add(ans,mult(get(uz),get(add(ar[i][0]-maxi,1LL))));
    ans=add(ans,mult(get(uz),mult(ar[i][0]-maxi,maxi)));
  }

  cout << ans << endl;
}

int32_t main(){
   

     cin.tie(0); ios::sync_with_stdio(0);
     cout << fixed <<  setprecision(15);
   
   int t=1;//cin>> t;
 
 for(int i=1;i<=t;i++)
 {
  //  cout << "Case #" << i << ": ";
    solve();
 }
 
 return 0;
}

Compilation message (stderr)

fancyfence.cpp:2: warning: ignoring '#pragma optimize ' [-Wunknown-pragmas]
    2 | #pragma optimize ("Bismillahirrahmanirrahim")
      |

• 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