#include<bits/stdc++.h> using namespace std; int _,n,a[200005],vis[200005],ans[200005]; inline int ck(int x){ int l=1,r=n; while(l<=r){ if(a[l]==a[r])l++,r--; else if(a[l]==x)l++; else if(a[r]==x)r--; else return 0; } return 1; } int main(){ scanf("%d",&_); while(_--){ scanf("%d",&n); long long sum=0; for(int i=1;i<=n;i++){ scanf("%d",&a[i]); vis[a[i]]++; if(vis[a[i]]==1)sum++; } long long flag=1; for(int i=1;i<=n;i++){ if(a[i]!=a[n-i+1]){ flag=0; break; } } if(flag==1){ printf("%lld\n",sum); for(int i=1;i<=n;i++){ if(vis[i])printf("%lld ",i),vis[i]=0; } printf("\n"); continue; } long long l=1,r=n; while(l<=r){ vis[a[l]]=vis[a[r]]=0; if(a[l]!=a[r]){ if(ck(a[l]) && ck(a[r])){ printf("2\n%lld %lld\n",min(a[l],a[r]),max(a[l],a[r])); } else if(ck(a[l])){ printf("1\n%lld\n",a[l]); } else if(ck(a[r])){ printf("1\n%lld\n",a[r]); } else{ printf("0\n\n"); } break; } l++,r--; } } }