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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3. #define int              long long int
  4. #define double           long double
  5. #define print(a)         for(auto x : a) cout << x << " "; cout << endl
  6.  
  7.  
  8. const int M = 1000000007;
  9. const int N = 3e5+9;
  10. const int INF = 2e9+1;
  11. const int LINF = 2000000000000000001;
  12.  
  13. inline int power(int a, int b, int mod=M) {
  14.     int x = 1;
  15.     a %= mod;
  16.     while (b) {
  17.         if (b & 1) x = (x * a) % mod; 
  18.         a = (a * a) % mod;
  19.         b >>= 1;
  20.     }
  21.     return x;
  22. }
  23.  
  24.  
  25. //_ ***************************** START Below *******************************
  26.  
  27. //* Change this to false => before submitting to cf
  28. // bool testing = true; 
  29. bool testing = false;
  30.  
  31.  
  32. vector<int> a = {INF, 2, 4, 3, 7, 10, 11, 1, 9, 8, 6, 5};
  33.  
  34. int  interactor(int i){
  35.     return a[i];
  36. }
  37.  
  38. //*    n = 11
  39. //*  [  inf   2   4   3   7  10  11  1  9   8   6   5   inf   ]
  40.  
  41.  
  42. int askQuery(int x){
  43.     cout << "? " << x << endl;
  44.  
  45.     if(testing){
  46.         cout << interactor(x) << endl;
  47.         return interactor(x);
  48.     }
  49.     int y;
  50.     cin >> y;
  51.     return y;
  52.  
  53. }
  54.  
  55.  
  56. int consistency(){
  57.  
  58.     int n;
  59.     cin >> n;
  60.  
  61.  
  62.     int s = 1, e = n;
  63.     int ans = -1;
  64.  
  65.     while(s<=e){
  66.         int mid = s + (e-s)/2;
  67.  
  68.  
  69.         int res = askQuery(mid);
  70.         int left = mid-1 == 0 ? INF : askQuery(mid-1);
  71.         int right = mid+1 == n+1 ? INF : askQuery(mid+1);
  72.  
  73.         if(left > res && res < right){
  74.             ans = mid;
  75.             break;
  76.         }
  77.         if(left > res ){
  78.             s = mid+1;
  79.         }
  80.         else{
  81.             e = mid-1;
  82.         }
  83.  
  84.     }
  85.  
  86.     return ans;
  87. }
  88.  
  89.  
  90.  
  91.  
  92.  
  93.  
  94.  
  95.  
  96. void solve() {
  97.  
  98.     int ans = consistency();
  99.     cout << "! " << ans << endl;
  100.  
  101. }
  102.  
  103.  
  104.  
  105.  
  106.  
  107. int32_t main() {
  108.     ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  109.  
  110.     solve();
  111.  
  112.     return 0;
  113. }
Success #stdin #stdout 0s 5324KB
comments (?)
stdin
copy 
11
stdout
copy 
? 6
11
? 5
10
? 7
1
? 3
3
? 2
4
? 4
7
! 3
https://ideone.com/frrPtP
language:
C++14 (gcc 8.3)
created:
18 hours ago
visibility:
public

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