Language: C++

/*
                                                                                                     
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                                               ``````                                               
*/
#pragma GCC optimize("O3")
#pragma GCC optimize("avx2")
#pragma GCC optimize("unroll-loops")
#include <iostream>
#include <iostream>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <tuple>
#include <math.h>
#include <set>
#include <stack>
#include <bitset>
#include <map>
#include <queue>
#include <random>
#include <unordered_set>
#include <unordered_map>
#define DEBUG
#define fi first
#define se second
#define pqueue priority_queue
#define pb(x) push_back(x)
//#define endl '\n'
#define all(x) x.begin(), x.end()
// #define int long  long
#define mk(a, b) make_pair(a, b)
 
using namespace std;
      
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef vector<int> vi;
typedef vector<vector<int> > vvi;
typedef vector<ull> vull;
typedef vector<ll> vll;
// typedef tuple<ll, ll, ll> tiii;
typedef pair<int, int> pii;
typedef vector<pair<int, int> > vpii;
typedef vector<bool> vb;
typedef vector<string> vs;
typedef vector< vector<ll> > vvll;
typedef vector<char> vc;
      
const int INF = 1e9 + 228;
const ll INFLL = 1e18;
const ll MOD = 1e9 + 7;
//static const int maxn = 1e6 + 228;
const ld eps = 1e-6;
const ld eps2 = 1e-9;
const ll MOD2 = 998244353;
const ll dosz = 5e5;
const ll SZ = (1<<18);
const ld PI = atan2l(0, -1);
     
void fast_io(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    // freopen("a.in", "r", stdin);
//    freopen("logs.out", "w", stdout);
}

void solve(){
    string s;
    cin >> s;
    int ans = n;
    int n = s.size();
    for(int i=0; i+1<n; i++){
        if(s[i]!=s[i+1])
            ans = min(ans, max(i+1, n-i-1));
    }
    cout << ans << endl;
}
 
signed main(){
    fast_io();
    srand(time(NULL));
    cout << fixed << setprecision(12);
    int q = 1;
    // cin >> q;
    while(q--)
        solve();
     
}

Compiler output:
a.cc:57:28: warning: bad option '-favx2' to pragma 'optimize' [-Wpragmas]
   57 | #pragma GCC optimize("avx2")
      |                            ^
a.cc:112:14: warning: bad option '-favx2' to attribute 'optimize' [-Wattributes]
  112 | void fast_io(){
      |              ^
a.cc:119:12: warning: bad option '-favx2' to attribute 'optimize' [-Wattributes]
  119 | void solve(){
      |            ^
a.cc: In function 'void solve()':
a.cc:122:15: error: 'n' was not declared in this scope
  122 |     int ans = n;
      |               ^
a.cc: At global scope:
a.cc:131:13: warning: bad option '-favx2' to attribute 'optimize' [-Wattributes]
  131 | signed main(){
      |             ^