API tools faq
paste
Advertisement
tepyotin2

Binary Search

tepyotin2
Jul 4th, 2025
313
0
Never
Add comment
Not a member of Pastebin yet? Sign Up, it unlocks many cool features!
C++ 1.88 KB | None | 0 0
raw download clone embed print report
  1. #include <bits/stdc++.h>
  2.  
  3. using namespace std;
  4.  
  5. struct Swap{
  6.     int a, b;
  7. };
  8.  
  9. int t;
  10.  
  11. void solve(){
  12.     int n, x;
  13.     cin >> n >> x;
  14.     // cout << "n: " << n << ", x: " << x << '\n';
  15.     vector<int> perm(n+1);
  16.     vector<Swap> sw;
  17.     int pos_x = -1;
  18.     for(int i=1; i<=n; i++){
  19.         cin >> perm[i];
  20.         if(perm[i] == x){
  21.             pos_x = i;
  22.         }
  23.     }
  24.     // for(int i=1; i<=n; i++){
  25.     //     if(perm[i] == x){
  26.     //         pos_x = i;
  27.     //     }
  28.     // }
  29.     int l = 1;
  30.     int r = n+1;
  31.     while(r-l>1){
  32.         int m = (r+l)/2;
  33.         if(perm[m]<=x){
  34.             l = m;
  35.         }else{
  36.             r = m;
  37.         }
  38.     }
  39.     // cout << "l: " << l << ", r: " << r << '\n';
  40.     if(perm[l] == x){
  41.         cout << "0" << '\n';
  42.         return;
  43.     }
  44.     if(l != pos_x){
  45.         // cout << "HI" << '\n';
  46.         // cout << "l: " << l << ", " << pos_x << '\n';
  47.         sw.push_back({l, pos_x});
  48.         swap(perm[l], perm[pos_x]);
  49.     }
  50.     // for(int i=1; i<=n; i++){
  51.     //     cout << perm[i] << '\n';
  52.     // }
  53.     int nl = 1;
  54.     int nr = n+1;
  55.     while(nr-nl>1){
  56.         int m = (nr+nl)/2;
  57.         if(perm[m]<=x){
  58.             nl = m;
  59.         }else{
  60.             nr = m;
  61.         }
  62.     }
  63.     // cout << "nl: " << nl << ", nr: " << nr << '\n';
  64.     if(perm[nl] == x){
  65.         cout << sw.size() << '\n';
  66.         for(Swap v: sw){
  67.             cout << v.a << " " << v.b << '\n';
  68.         }
  69.         return;
  70.     }
  71.     for(int i=1; i<=n; i++){
  72.         if(i!=l && i!=pos_x && perm[i] == l){
  73.             sw.push_back({i, l});
  74.             cout << sw.size() << '\n';
  75.             for(Swap v: sw){
  76.                 cout << v.a << " " << v.b << '\n';
  77.             }
  78.             return;
  79.         }
  80.     }
  81. }
  82.  
  83. int main(){
  84.     // freopen("binarysearch.in", "r", stdin);
  85.  
  86.     cin >> t;
  87.     while(t--){
  88.         solve();
  89.     }
  90.  
  91.     return 0;
  92. }
Advertisement
Add Comment
Please, Sign In to add comment
Advertisement
Public Pastes
Advertisement
We use cookies for various purposes including analytics. By continuing to use Pastebin, you agree to our use of cookies as described in the Cookies Policy.  OK, I Understand
Not a member of Pastebin yet?
Sign Up, it unlocks many cool features!