distinct_split.cpp

#include <iostream>
#include <bits/stdc++.h>
#define ll long long
#define pb push_back
#define fast_io ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define fr(i,a,b) for (int i =a;i<b;i++)
#define loop(x,n) for (int x = 0;x<n;++x)
#define mod 1000000007
#define inf (1LL<<60)
#define all(x) (x).begin(), (x).end()

using namespace std;

void precal(){

}

void solve (){
    int n;
    cin>>n;
    string s;
    cin>>s;
    map <char,int> a, b ;
    for (int i=0;i<n;i++){
        b[s[i]]++;
    }
    int maxindex = 0,valmax =0;
    for (int i =0;i<n-1;i++){
        a[s[i]]++; b[s[i]]--;
        if(b[s[i]]==0){
            auto iter =  b.find(s[i]);
            b.erase(iter);
        }
        if(b.size()+a.size()>valmax){
            valmax = a.size()+b.size();
            maxindex = i;
        }   
    }
    cout<<valmax<<"\n";
}

int main(){
    fast_io;
    cout<<fixed;
    cout<< setprecision(10);
    precal();
    int t =1;
    cin>> t ;
    for (int i =1;i<=t;i++){
        // cout<< "Case #"<<i<<": ";
        solve();
    }

    return 0;

}