11572 - Unique Snowflakes

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1000000+5;
int T,n,A[maxn];
int main(){
    scanf("%d",&T);
    while(T--){
        scanf("%d",&n);
        for(int i=0;i<n;i++) scanf("%d",&A[i]);
        set<int> s;
        int L = 0,R = 0,ans = 0;
        while(R<n) {
            while(R<n&&!s.count(A[R])) s.insert(A[R++]);
            ans = max(ans,R-L);
            s.erase(A[L++]);
        }
        printf("%d\n",ans);
    }
    return 0;
}