Language: C++

#include <bits/stdc++.h>
using namespace std;

#define Mset(s, n)      memset(s, n, sizeof(s))
#define Rp0(i, m)       for(int i = 0; i < m; ++i)
#define Rpd(i, m, l)    for(int i = l; i >= m; --i)
#define Rp1(i ,m)       for(int i = 1; i <= m; i++)
#define All(a)          (a).begin(), (a).end()
#define Lwb             lower_bound
#define Upb             upper_bound
#define Sz(a)           int((a).size())
#define u_map           unordered_map
#define Exist(a, b)     (find(All(a), (b)) != (a).end())
#define Sort(x)         sort(All(x))
#define Gsort(x)        sort(All(x), greater<typeof(*((x).begin()))>())
#define Unique(v)       Sort(v); (v).resize(unique(ALL(v)) - (v).begin())

#define fi              first
#define se              second
#define pb              push_back
#define pf              push_front
#define is              insert
#define ooi             INT_MAX
#define ool             LLONG_MAX
#define ll              long long
#define ull             unsigned ll
#define ld              long double
#define pii             pair<int, int>
#define vi              vector<int>
#define vpii            vector<pii>

const ll MOD = (ll) 1e9 + 7;
const ld PI = acos((ld) -1);
inline int Get_bit(int x, int k){return (x >> (k - 1)) & 1;}
inline ll Gcd(ll a, ll b) {ll r; while(b){ r = a % b; a = b; b = r;} return a;}
inline ll Lcm(ll a, ll b) {return a / Gcd(a, b) * b;}
inline ll Pow(ll n, ll k) {ll r = 1; for(; k; k >>= 1, n = n * n % MOD){if(k & 1) r = r * n % MOD;} return r;}


const int N = 5e3 + 10;

struct RollingHash {
    static const int base1 = 1007, base2 = 2009;
    static const int mod1 = 1000000007, mod2 = 1000000009;
    vector<long long> hash1, hash2, power1, power2;

    // construct
    RollingHash(const string &S) {
        int n = (int)S.size();
        hash1.assign(n, 0);
        hash2.assign(n, 0);
        power1.assign(n, 1);
        power2.assign(n, 1);
        for(int i = 1; i < n; ++i) {
            hash1[i] = (hash1[i - 1] * base1 + S[i]) % mod1;
            hash2[i] = (hash2[i - 1] * base2 + S[i]) % mod2;
            power1[i] = (power1[i - 1] * base1) % mod1;
            power2[i] = (power2[i - 1] * base2) % mod2;
        }
    }

    // get hash of S[left:right]
    inline pair<long long, long long> Get(int l, int r) const {
        long long res1 = hash1[r] - hash1[l - 1] * power1[r - l + 1] % mod1;
        if (res1 < 0) res1 += mod1;
        long long res2 = hash2[r] - hash2[l - 1] * power2[r - l + 1] % mod2;
        if (res2 < 0) res2 += mod2;
        return {res1, res2};
    }
};

int n, m, k, q, ans;

void Solve(){
    string s;
    cin >> n >> s;
    s = ' ' + s;
    RollingHash rh(s);
    for(int k = (n + 1) / 2; k >= 1; k--){
        unordered_map<pair<ll, ll>, int> mp;
        for(int i = 1; i <= n - k + 1; i++){
            pair<ll, ll> x = rh.Get(i, i + k - 1);
            if(mp[x] == 0){
                mp[x] = i + k - 1;
            } else if(mp[x] < i){
                cout << k;
                exit(0);
            }
        }
    }
    cout << 0;
}

int main(){
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(10);
    Solve();
}


Compiler output:
a.cc: In function 'void Solve()':
a.cc:80:42: error: use of deleted function 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map() [with _Key = std::pair<long long int, long long int>; _Tp = int; _Hash = std::hash<std::pair<long long int, long long int> >; _Pred = std::equal_to<std::pair<long long int, long long int> >; _Alloc = std::allocator<std::pair<const std::pair<long long int, long long int>, int> >]'
   80 |         unordered_map<pair<ll, ll>, int> mp;
      |                                          ^~
In file included from /usr/include/c++/14/unordered_map:41,
                 from /usr/include/c++/14/functional:63,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:53,
                 from a.cc:1:
/usr/include/c++/14/bits/unordered_map.h:148:7: note: 'std::unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map() [with _Key = std::pair<long long int, long long int>; _Tp = int; _Hash = std::hash<std::pair<long long int, long long int> >; _Pred = std::equal_to<std::pair<long long int, long long int> >; _Alloc = std::allocator<std::pair<const std::pair<long long int, long long int>, int> >]' is implicitly deleted because the default definition would be ill-formed:
  148 |       unordered_map() = default;
      |       ^~~~~~~~~~~~~
/usr/include/c++/14/bits/unordered_map.h: At global scope:
/usr/include/c++/14/bits/unordered_map.h:148:7: error: use of deleted function 'std::_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::_Hashtable() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _Alloc = std::allocator<std::pair<const std::pair<long long int, long long int>, int> >; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<long long int, long long int> >; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _RehashPolicy = std::__detail::_Prime_rehash_policy; _Traits = std::__detail::_Hashtable_traits<true, false, true>]'
In file included from /usr/include/c++/14/bits/unordered_map.h:33:
/usr/include/c++/14/bits/hashtable.h:539:7: note: 'std::_Hashtable<_Key, _Value, _Alloc, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _RehashPolicy, _Traits>::_Hashtable() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _Alloc = std::allocator<std::pair<const std::pair<long long int, long long int>, int> >; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<long long int, long long int> >; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _RehashPolicy = std::__detail::_Prime_rehash_policy; _Traits = std::__detail::_Hashtable_traits<true, false, true>]' is implicitly deleted because the default definition would be ill-formed:
  539 |       _Hashtable() = default;
      |       ^~~~~~~~~~
/usr/include/c++/14/bits/hashtable.h:539:7: error: use of deleted function 'std::__detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _Traits>::_Hashtable_base() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<long long int, long long int> >; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _Traits = std::__detail::_Hashtable_traits<true, false, true>]'
In file included from /usr/include/c++/14/bits/hashtable.h:35:
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: note: 'std::__detail::_Hashtable_base<_Key, _Value, _ExtractKey, _Equal, _Hash, _RangeHash, _Unused, _Traits>::_Hashtable_base() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _ExtractKey = std::__detail::_Select1st; _Equal = std::equal_to<std::pair<long long int, long long int> >; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; _Traits = std::__detail::_Hashtable_traits<true, false, true>]' is implicitly deleted because the default definition would be ill-formed:
 1731 |       _Hashtable_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: error: use of deleted function 'std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Hash, _RangeHash, _Unused, __cache_hash_code>::_Hash_code_base() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _ExtractKey = std::__detail::_Select1st; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; bool __cache_hash_code = true]'
/usr/include/c++/14/bits/hashtable_policy.h: In instantiation of 'std::__detail::_Hashtable_ebo_helper<_Nm, _Tp, true>::_Hashtable_ebo_helper() [with int _Nm = 1; _Tp = std::hash<std::pair<long long int, long long int> >]':
/usr/include/c++/14/bits/hashtable_policy.h:1328:7:   required from here
 1328 |       _Hash_code_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1245:49: error: use of deleted function 'std::hash<std::pair<long long int, long long int> >::hash()'
 1245 |       _Hashtable_ebo_helper() noexcept(noexcept(_Tp())) : _Tp() { }
      |                                                 ^~~~~
In file included from /usr/include/c++/14/string_view:50,
                 from /usr/include/c++/14/bits/basic_string.h:47,
                 from /usr/include/c++/14/string:54,
                 from /usr/include/c++/14/bitset:52,
                 from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:52:
/usr/include/c++/14/bits/functional_hash.h:102:12: note: 'std::hash<std::pair<long long int, long long int> >::hash()' is implicitly deleted because the default definition would be ill-formed:
  102 |     struct hash : __hash_enum<_Tp>
      |            ^~~~
/usr/include/c++/14/bits/functional_hash.h:102:12: error: no matching function for call to 'std::__hash_enum<std::pair<long long int, long long int>, false>::__hash_enum()'
/usr/include/c++/14/bits/functional_hash.h:83:7: note: candidate: 'std::__hash_enum<_Tp, <anonymous> >::__hash_enum(std::__hash_enum<_Tp, <anonymous> >&&) [with _Tp = std::pair<long long int, long long int>; bool <anonymous> = false]'
   83 |       __hash_enum(__hash_enum&&);
      |       ^~~~~~~~~~~
/usr/include/c++/14/bits/functional_hash.h:83:7: note:   candidate expects 1 argument, 0 provided
/usr/include/c++/14/bits/functional_hash.h:102:12: error: 'std::__hash_enum<_Tp, <anonymous> >::~__hash_enum() [with _Tp = std::pair<long long int, long long int>; bool <anonymous> = false]' is private within this context
  102 |     struct hash : __hash_enum<_Tp>
      |            ^~~~
/usr/include/c++/14/bits/functional_hash.h:84:7: note: declared private here
   84 |       ~__hash_enum();
      |       ^
/usr/include/c++/14/bits/hashtable_policy.h:1245:49: note: use '-fdiagnostics-all-candidates' to display considered candidates
 1245 |       _Hashtable_ebo_helper() noexcept(noexcept(_Tp())) : _Tp() { }
      |                                                 ^~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1328:7: note: 'std::__detail::_Hash_code_base<_Key, _Value, _ExtractKey, _Hash, _RangeHash, _Unused, __cache_hash_code>::_Hash_code_base() [with _Key = std::pair<long long int, long long int>; _Value = std::pair<const std::pair<long long int, long long int>, int>; _ExtractKey = std::__detail::_Select1st; _Hash = std::hash<std::pair<long long int, long long int> >; _RangeHash = std::__detail::_Mod_range_hashing; _Unused = std::__detail::_Default_ranged_hash; bool __cache_hash_code = true]' is implicitly deleted because the default definition would be ill-formed:
 1328 |       _Hash_code_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1328:7: error: use of deleted function 'std::__detail::_Hashtable_ebo_helper<1, std::hash<std::pair<long long int, long long int> >, true>::~_Hashtable_ebo_helper()'
/usr/include/c++/14/bits/hashtable_policy.h:1242:12: note: 'std::__detail::_Hashtable_ebo_helper<1, std::hash<std::pair<long long int, long long int> >, true>::~_Hashtable_ebo_helper()' is implicitly deleted because the default definition would be ill-formed:
 1242 |     struct _Hashtable_ebo_helper<_Nm, _Tp, true>
      |            ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1242:12: error: use of deleted function 'std::hash<std::pair<long long int, long long int> >::~hash()'
/usr/include/c++/14/bits/functional_hash.h:102:12: note: 'std::hash<std::pair<long long int, long long int> >::~hash()' is implicitly deleted because the default definition would be ill-formed:
  102 |     struct hash : __hash_enum<_Tp>
      |            ^~~~
/usr/include/c++/14/bits/functional_hash.h:102:12: error: 'std::__hash_enum<_Tp, <anonymous> >::~__hash_enum() [with _Tp = std::pair<long long int, long long int>; bool <anonymous> = false]' is private within this context
/usr/include/c++/14/bits/functional_hash.h:84:7: note: declared private here
   84 |       ~__hash_enum();
      |       ^
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: note: use '-fdiagnostics-all-candidates' to display considered candidates
 1731 |       _Hashtable_base() = default;
      |       ^~~~~~~~~~~~~~~
/usr/include/c++/14/bits/hashtable_policy.h:1731:7: error: use of deleted function 'std::__detail::_Hash_code_base<std::pair<long long int, long long int>, std::pair<const std::pair<long long int, long long int>, int>, std::__detail::_Select1st, std::hash<std::pair<long long int, long long int> >, std::__detail::_Mod_range_hashing, std::__detail::_D