https://www.luogu.com.cn/problem/UVA11572

cpp
#include<bits/stdc++.h>
using namespace std;
// #define int long long 
const int M=2e5+5;
int a[M];
pair<int,int>f[M];
int dp[M][21];
int lo[M];
void solve(){
    int n;
    cin>>n;
    for(int i=1;i<=n;++i)cin>>a[i];
    map<int,int>cnt;
    int l=1,r=0;
    int ans=0;
    while(l<=n&&r<=n){
        while (r<n)
        {
            if(cnt[a[r+1]]==1)break;
            r++;
            cnt[a[r]]++;
        }
        ans=max(ans,r-l+1);
        // cout<<l<<' '<<r<<endl;
        cnt[a[l]]--;
        l++;
    }
    cout<<ans<<endl;
}
signed main(){
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
    int t=1;
    cin>>t;
    while(t--)solve();
	return 0;
}