1791 C. Prepend and Append.cpp

/*
problem link: https://codeforces.com/contest/1791/problem/C
my solution on codeforces : https://codeforces.com/contest/1791/submission/192803396
problem name: C. Prepend and Append
status: accepted
author:  LELLO 
*/
#include <bits/stdc++.h>
#include <iostream>
#include <chrono>
#include <vector>
#include <set>
#include <map>
#include<math.h>
#include <stack>
#include <cmath>
#include <unordered_map>
#include <algorithm>
#include <iomanip>
#include <bitset>
#include <utility>
#include <string>
#include <cctype>
#include <iomanip>
#include <numeric> // for NTH
#define bye return;
#define endl '\n'
#define ll long long
#define li long int
#define lli long long int
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) ((x).size())
#define ison(num, bit) (num & (1 << bit))
#define setoffif(num, bit) (num ^= (1 << bit)) // iff (num &(1<<bit))
#define setoff(num, bit) (num &= ~(1 << bit))
#define seton(num, bit) (num |= (1 << bit))
#define flipbit(num, bit) (num ^= (1 << bit))
#define LSB(num) (num & (-num))
#define pop_count_int(num) __builtin_popcount(num)
#define pop_count_l(num) __builtin_popcountl(num)
#define pop_count_ll(num) __builtin_popcountll(num)
#define clz(num) __builtin_clz(num)
#define clzll(num) __builtin_clzll(num)
#define ctz(num) __builtin_ctz(num)
#define ctzll __builtin_ctzll
#define Num_of_Digits(n) ((ll)log10(n) + 1)
#define ceill(n, m) (((n) / (m)) + (((n) % (m) ) ? 1 : 0))
#define lastOne(x) (__builtin_clzll(x))
#define fixed(n) fixed << setprecision(n)
#define lb(c, x) distance((c).begin(), lower_bound(all(c), (x)))
#define ub(c, x) distance((c).begin(), upper_bound(all(c), (x)))
#define Time cerr << "Time Taken: " << (float)clock() / CLOCKS_PER_SEC << " Secs" << "\n";
#define Pi  3.14159265358979323846264
#define INF 0x3f3f3f3f
#define sin(a) sin((a)*PI/180)
#define cos(a) cos((a)*PI/180)
#define yes cout << "YES" << endl;
#define no cout << "NO" << endl;
#define M 32
ll sgn(ll x){ if(x > 0) return 1; if(x < 0) return -1; return 0;}
ll mod = 1e9 + 7;
ll mul(ll a, ll b) { return ((a % mod) * (b % mod)) % mod; }
ll add(ll a, ll b) { return ((a % mod) + (b % mod)) % mod; }
ll sub(ll a, ll b) { return ((a % mod) - (b % mod) + mod) % mod; }
using namespace std;
void AC() {
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr); // or cin.tie(NULL)
    cout.tie(nullptr);  // or cout.tie(0)
}
void file_set(){ //string& file_name
    #ifndef ONLINE_JUDGE
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
    // freopen((file_name+".in").c_str(), "r", stdin);
    // freopen((file_name+".out").c_str(), "w", stdout);
}
bool sortbysec(const pair<int,int> &a,const pair<int,int> &b)
{
    return (a.second < b.second);
}
    // THOSE WHO CAN'T REMEMBER THE PAST'RE CONDEMNED TO REPEAT IT (USE DP -_-) - George Santayana
    // PUSH HARDER THAN YESTERDAY IF YOU WANT A DIFFERENT TOMORROW !
    //YOU DON'T HAVE TO BE A GENIUS , YOU NEED TO BE DETERMINED .
const ll int MAX = 6e6;
ll int dp[MAX] ;
const ll LOO = 0x3f3f3f3f3f3f3f3f;
const int OO = 0x3f3f3f3f;
void LELLO(){
    int n ; cin >> n ;
    string s ; cin >> s ;
    deque<char> de ;
    for (int i = 0; i < n; i++)
    {
        de.push_back(s[i]);
    }
    while (true)
    {
        if(de.empty()){
                cout<< 0 <<endl;
                bye
        }
        if((de.front() == '1' && de.back() == '0') || (de.front() == '0' && de.back() == '1') ){
            de.pop_front();
            de.pop_back();
        }else{
            cout<< de.size() <<endl;
            bye
        }
    }
}
void driver(ll t=1)
{
 
    while (t--) LELLO();
    Time 
}
signed main()
{
    AC();
    // file_set();
    ll test ; cin >> test ;
    // chrono::time_point<chrono::system_clock> start, end;
    // start = chrono::system_clock::now();
    driver(test);
    // end = chrono::system_clock::now();
    // chrono::duration<double> elapsed_seconds = end - start;
    // time_t end_time = chrono::system_clock::to_time_t(end);
    // cout << "finished computation at " << ctime(&end_time) << "elapsed time: " << elapsed_seconds.count() << "s\n";
}