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  1.  
  2. #include<bits/stdc++.h>
  3. #define li long long int
  4. #define ld long double
  5. #define all(v) v.begin(),v.end()
  6. #define rev(a) reverse(all(a))
  7. #define sort(a) sort(all(a))
  8. #define pb push_back
  9. #define INF 1e18+10
  10. #define MINF -1e18-10
  11. #define rep(i,a,b) for(li i=a;i<b;i++)
  12. #define vli vector<li>
  13. using namespace std;
  14.  
  15.  
  16. template <class T> void read(T& x){
  17.   cin>>x;
  18. }
  19.  
  20. template <class T, class... U> void read1(T& x, U&... u){
  21.   read(x);
  22.   read(u...);
  23. }
  24.  
  25. template <class A> void read1(vector<A>& v){
  26.   for(auto &it:v)
  27.     read(it);
  28. }
  29.  
  30.  
  31.  
  32.  
  33.  
  34. void solve()
  35. {
  36.     li n;
  37.     cin>>n;
  38.  
  39.     vli v(n);
  40.     read1(v);
  41.  
  42.     li gcd1 = 0;
  43.     gcd1 = v[0];
  44.     rep(i,0,n){
  45.       if(i+2 <= n-1){
  46.         gcd1 = __gcd(gcd1,v[i+2]);
  47.       }
  48.       i+=1;
  49.     }
  50.  
  51.     li gcd2 = 0;
  52.     if(n>1)
  53.     gcd2 = v[1];
  54.     rep(i,1,n){
  55.       if(i+2 <= n-1){
  56.         gcd2 = __gcd(gcd2,v[i+2]);
  57.       }
  58.       i+=1;
  59.     }
  60.  
  61.  
  62.  
  63.     if(gcd1==gcd2){
  64.       cout<<0<<endl;
  65.     }
  66.     else{
  67.       bool t1 = false, t2 = false, t3 = false;
  68.  
  69.       rep(i,0,n){
  70.         if(i%2==0 and v[i]%gcd1==0 ){
  71.           t1 = true;
  72.         }
  73.         if(i%2 and v[i]%gcd1==0){
  74.           t2 = true;
  75.         }
  76.       }
  77.  
  78.       if(t2 and t1)
  79.         t3 = true;
  80.       else if(gcd1>1){
  81.         cout<<gcd1<<endl;
  82.         return;
  83.       }
  84.  
  85.       t1 = false,t2 = false;
  86.       rep(i,0,n){
  87.         if(i%2==0 and v[i]%gcd2==0 ){
  88.           t1 = true;
  89.         }
  90.         if(i%2 and v[i]%gcd2==0){
  91.           t2 = true;
  92.         }
  93.       }
  94.  
  95.       if(t1 and t3 and t2)
  96.         cout<<0<<endl;
  97.       else if(gcd2>1)
  98.         cout<<gcd2<<endl;
  99.  
  100.     }
  101. }   
  102.  
  103. int main()
  104. {
  105.     ios_base::sync_with_stdio(false);
  106.     cin.tie(0);
  107.     cout.tie(0);
  108.  
  109.     #ifndef ONLINE_JUDGE
  110.      freopen("inputf.in", "r", stdin);
  111.      freopen("outputf.in", "w", stdout);
  112.     #endif
  113.  
  114.  
  115.     li tc;
  116.     cin>>tc;
  117.     rep(i,0,tc){ 
  118.       solve();  
  119.     }  
  120.  
  121.   return 0;
  122. }
Success #stdin #stdout 0s 5524KB
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stdout
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https://ideone.com/is9jh6
language:
C++14 (gcc 8.3)
created:
3 years ago
visibility:
public

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