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  1. #include <cmath>
  2. #include <cstdio>
  3. #include <vector>
  4. #include <iostream>
  5. #include <algorithm>
  6. #include <set>
  7. #define lli long long int
  8. using namespace std;
  9.  
  10. int main() {
  11.     int t;
  12.     cin>>t;
  13.     while(t--){
  14.         int n,k;
  15.         cin>>n>>k;
  16.         lli a[n];
  17.         vector<lli> left,unique;
  18.         for(int i=0;i<n;i++) cin>>a[i];
  19.         sort(a,a+n);
  20.         lli current=a[0];
  21.         //left stores only the repettive elements
  22.         //eg: if a = [1,2,2,3,3,3,4,4] then left = [2,3,3,4]
  23.         for(int i=1;i<n;i++){
  24.             if(a[i]==current) left.push_back(a[i]);
  25.             else current = a[i];
  26.         }
  27.         //set 's' stores unique elemts from array 'a'
  28.         set<lli> s;
  29.         for(int i=0;i<n;i++) s.insert(a[i]);
  30.         unique.assign(s.begin(),s.end());
  31.         //checks if value of 'k' is <= number of unique elements
  32.         if(unique.size()>=k){
  33.             cout<<"-1"<<endl;
  34.             continue;
  35.         }
  36.         //num stores the count of remaining elements we need to find other than unique
  37.         int num = k - unique.size();
  38.         //left already sorted, taking first 'num' elements from 'left' to make up k values
  39.         for(int i=0;i<num;i++){
  40.             unique.push_back(left[i]);
  41.         }
  42.         //unique is no more unique, but contains all the elements choosen to give
  43.         sort(unique.begin(),unique.end());
  44.         //rest of the procedure tries to find the best two sides if possible
  45.         lli x1,x2;
  46.         x1=unique[unique.size()-1];
  47.         bool flag=false,first_time=true,yes=false;
  48.         for(int i=unique.size()-2;i>=0;i--){
  49.             if(flag){
  50.                 if(first_time){
  51.                     x2=unique[i];    
  52.                     first_time=false;    
  53.                 } 
  54.                 else{
  55.                     if(unique[i]==x2) {yes=true;break;}
  56.                     else x2=unique[i];
  57.                 }
  58.             }
  59.             else{
  60.                 if(unique[i]!=x1) x1=unique[i];
  61.                 else {flag=true;first_time=true;}        
  62.             }
  63.         }
  64.         if(yes){
  65.             lli prod = x1*x2;
  66.             cout<<prod<<endl;    
  67.         }
  68.         else{
  69.             cout<<"-1"<<endl;
  70.         }
  71.  
  72.     }
  73.     return 0;
  74. }
Time limit exceeded #stdin #stdout 5s 4388KB
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https://ideone.com/viAZqo
language:
C++14 (gcc 8.3)
created:
5 years ago
visibility:
public

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