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  1. #include<bits/stdc++.h>
  2.  
  3. using namespace std;
  4. int main(){
  5.     int t; cin>>t;
  6.     while(t--){
  7.         int n,k; cin>>n>>k;
  8.         int arr[200005];
  9.         for(int i=0; i<n; ++i){
  10.             cin>>arr[i];
  11.         }
  12.         int preSum[400005];
  13.         for(int i=0; i<200005; ++i){
  14.             preSum[i] = 0;
  15.         }
  16.         for(int i=0;i<(n/2); ++i){
  17.             int mn = min(arr[i], arr[n-i-1]);
  18.             int mx = max(arr[i], arr[n-i-1]);
  19.  
  20.             int valMin = mn+1;
  21.             int valMax = min(k*2, mx+k);
  22.  
  23.             preSum[valMin]+= 1;
  24.             preSum[valMax]+= -1;
  25.         }
  26.         for(int i=1; i<400001; ++i){
  27.             preSum[i] = preSum[i] + preSum[i-1];
  28.         }
  29.         for(int i=0; i<(n/2); ++i){
  30.             preSum[arr[i]+arr[n-1-i]]+=1;
  31.         }
  32.         int mx = -1;
  33.         for(int i=1; i<=2*k; ++i){
  34.             mx = max(mx, preSum[i]);
  35.         }
  36.         cout<<(n-mx)<<"\n";
  37.     }
  38.     return 0;
  39. }
Success #stdin #stdout 0s 4372KB
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https://ideone.com/sb6eFB
language:
C++ (gcc 8.3)
created:
4 years ago
visibility:
public

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