Language: C++

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

// template {{{
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define mt make_tuple
#define lb lower_bound
#define ub upper_bound
#define f first
#define s second
#define resz resize

#define sz(x) int((x).size())
#define all(x) (x).begin(), (x).end()

#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define F0R(i, a) for (int i = 0; i < (a); i++)
#define FORd(i, a, b) for (int i = (b)-1; i >= (a); i--)
#define F0Rd(i, a) for (int i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto& a : x)

#define sort_by(x, y) sort(all(x), [&](const auto& a, const auto& b) { return y; })

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vll = vector<ll>;
using vvll = vector<vll>;
using vb = vector<bool>;
using vd = vector<double>;
using vs = vector<string>;

using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;

using vpii = vector<pii>;
using vvpii = vector<vpii>;
using vpll = vector<pll>;
using vvpll = vector<vpll>;
using vpdd = vector<pdd>;
using vvpdd = vector<vpdd>;

template<typename T> void ckmin(T& a, const T& b) { a = min(a, b); }
template<typename T> void ckmax(T& a, const T& b) { a = max(a, b); }

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());

namespace __input {
    template<class T1, class T2> void re(pair<T1,T2>& p);
    template<class T> void re(vector<T>& a);
    template<class T, size_t SZ> void re(array<T,SZ>& a);

    template<class T> void re(T& x) { cin >> x; }
    void re(double& x) { string t; re(t); x = stod(t); }
    template<class Arg, class... Args> void re(Arg& first, Args&... rest) {
        re(first); re(rest...);
    }

    template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
    template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
    template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}
using namespace __input;

namespace __output {
    template<class T1, class T2> void pr(const pair<T1,T2>& x);
    template<class T, size_t SZ> void pr(const array<T,SZ>& x);
    template<class T> void pr(const vector<T>& x);
    template<class T> void pr(const deque<T>& x);
    template<class T> void pr(const set<T>& x);
    template<class T1, class T2> void pr(const map<T1,T2>& x);

    template<class T> void pr(const T& x) { cout << x; }
    template<class Arg, class... Args> void pr(const Arg& first, const Args&... rest) {
        pr(first); pr(rest...);
    }

    template<class T1, class T2> void pr(const pair<T1,T2>& x) {
        pr("{",x.f,", ",x.s,"}");
    }
    template<class T, bool pretty = true> void prContain(const T& x) {
        if (pretty) pr("{");
        bool fst = 1; for (const auto& a: x) pr(!fst?pretty?", ":" ":"",a), fst = 0;
        if (pretty) pr("}");
    }
    template<class T> void pc(const T& x) { prContain<T, false>(x); pr("\n"); }
    template<class T, size_t SZ> void pr(const array<T,SZ>& x) { prContain(x); }
    template<class T> void pr(const vector<T>& x) { prContain(x); }
    template<class T> void pr(const deque<T>& x) { prContain(x); }
    template<class T> void pr(const set<T>& x) { prContain(x); }
    template<class T1, class T2> void pr(const map<T1,T2>& x) { prContain(x); }

    void ps() { pr("\n"); }
    template<class Arg> void ps(const Arg& first) {
        pr(first); ps();
    }
    template<class Arg, class... Args> void ps(const Arg& first, const Args&... rest) {
        pr(first," "); ps(rest...);
    }
}
using namespace __output;

#define TRACE(x) x
#define __pn(x) pr(#x, " = ")
#define pd(...) __pn((__VA_ARGS__)), ps(__VA_ARGS__), cout << flush

namespace __algorithm {
    template<typename T> void dedup(vector<T>& v) {
        sort(all(v)); v.erase(unique(all(v)), v.end());
    }
    template<typename T> typename vector<T>::iterator find(vector<T>& v, const T& x) {
        auto it = lower_bound(all(v), x); return it != v.end() && *it == x ? it : v.end();
    }
    template<typename T> size_t index(vector<T>& v, const T& x) {
        auto it = find(v, x); assert(it != v.end() && *it == x); return it - v.begin();
    }
    template<typename C, typename T, typename OP> vector<T> prefixes(const C& v, T id, OP op) {
        vector<T> r(sz(v)+1, id); F0R (i, sz(v)) r[i+1] = op(r[i], v[i]); return r;
    }
    template<typename C, typename T, typename OP> vector<T> suffixes(const C& v, T id, OP op) {
        vector<T> r(sz(v)+1, id); F0Rd (i, sz(v)) r[i] = op(v[i], r[i+1]); return r;
    }
}
using namespace __algorithm;

struct monostate {
    friend istream& operator>>(istream& is, const __attribute__((unused))monostate& ms) { return is; }
    friend ostream& operator<<(ostream& os, const __attribute__((unused))monostate& ms) { return os; }
} ms;

template<typename W=monostate> struct wedge {
    int u, v, i; W w;
    wedge<W>(int _u=-1, int _v=-1, int _i=-1) : u(_u), v(_v), i(_i) {}
    int operator[](int loc) const { return u ^ v ^ loc; }
    friend void re(wedge& e) { re(e.u, e.v, e.w); --e.u, --e.v; }
    friend void pr(const wedge& e) { pr(e.u, "<-", e.w, "->", e.v); }
};

namespace __io {
    void setIn(string s) { freopen(s.c_str(),"r",stdin); }
    void setOut(string s) { freopen(s.c_str(),"w",stdout); }
    void setIO(string s = "") {
        ios_base::sync_with_stdio(0); cin.tie(0); cout.precision(15);
        if (sz(s)) { setIn(s+".in"), setOut(s+".out"); }
    }
}
using namespace __io;
// }}}

// {{{
struct suffix_array {
    const int INF = 0x7fffffff;

    int L, D;
    string str;
    vector<vi> suff;
    vi rank_of, at_rank;

    pair<pair<int, int>, int> __make_rep(int l, int i, int p) {
        if(!l) return {{str[i], INF}, i};
        return {{suff[l-1][i], (i+p<L) ? suff[l-1][i+p] : INF}, i};
    }

    suffix_array(string _str) {
        str = _str;
        L = str.size();
        D = 33 - __builtin_clz(L-1);
        suff.resize(D);

        vector<pair<pair<int, int>, int>> keys(L);
        for (int l = 0; l < D; l++) {
            for (int i = 0; i < L; i++)
                keys[i] = __make_rep(l, i, l? 1<<(l-1) : 0);
            sort(keys.begin(), keys.end());

            suff[l].resize(L);
            for (int i = 0, r = 0; i < L; i++) {
                if(i > 0 && keys[i].first != keys[i-1].first) r++;
                suff[l][keys[i].second] = r;
            }
        }

        rank_of.resize(L);
        at_rank.resize(L);
        for (int i = 0; i < L; i++) {
            rank_of[i] = suff.back()[i];
            at_rank[rank_of[i]] = i;
        }
    }

    // compare the string at [i, i+l1) to the string at [j, j+l2)
    int comp(int i, int l1, int j, int l2) {
        int cl = min(l1, l2);
        for (int l = 0; l < D; l++)
            if ((cl>>l)&1) {
                if(suff[l][i] != suff[l][j])
                    return suff[l][i] < suff[l][j] ? -1 : 1;
                i += 1<<l, j += 1<<l;
            }

        return (l1!=l2) ? (l1<l2) ? -1 : 1 : 0;
    }

    // find the interval of suffix ranks corresponding to instances of the substring at [i, i+len)
    pair<int, int> find_range(int i, int len) {
        int left = rank_of[i];
        for (int lo = 0, hi = left; lo <= hi; ) {
            int mi = (lo + hi)/2;
            if (at_rank[mi] + len <= L && comp(i, len, at_rank[mi], len) == 0) {
                left = mi;
                hi = mi-1;
            }
            else lo = mi+1;
        }

        int right = rank_of[i];
        for (int lo = right, hi = L-1; lo <= hi; ) {
            int mi = (lo + hi)/2;
            if (at_rank[mi] + len <= L && comp(i, len, at_rank[mi], len) == 0) {
                right = mi;
                lo = mi+1;
            }
            else hi = mi-1;
        }

        return make_pair(left, right);
    }
};
// }}}

// segment_tree {{{
template<typename T, typename F> struct segment_tree {
    int SZ;
    T id; F tt;
    vector<T> table;

    segment_tree() {}
    segment_tree(int _SZ, T _id, F _tt) : SZ(_SZ), id(_id), tt(_tt) {
        table.resize(2 * SZ, id);
    }
    template<typename L> void set_leaves(L create) {
        F0R (i, SZ) table[SZ + i] = create(i);
        FORd (i, 1, SZ) table[i] = tt(table[2 * i], table[2 * i + 1]);
    }

    // Replaces the element at index i with v
    void replace(int i, T v) {
        table[i += SZ] = v;
        for (i /= 2; i > 0; i /= 2) {
            table[i] = tt(table[2 * i], table[2 * i + 1]);
        }
    }

    // Accumulates the elements at indices in [i, j)
    T operator()(int i, int j) const {
        T left = id, right = id;
        for (i += SZ, j += SZ; i < j; i /= 2, j /= 2) {
            if (i&1) left = tt(left, table[i++]);
            if (j&1) right = tt(table[--j], right);
        }
        return tt(left, right);
    }
    const T& operator[](int i) const { return table[SZ + i]; }
};

template<typename T, typename F> struct full_segment_tree : segment_tree<T, F> {
    // Internal size is rounded up so that all layers are full
    full_segment_tree() {}
    full_segment_tree(int _SZ, T _id, F _tt) :
        segment_tree<T, F>(1 << (32 - __builtin_clz(_SZ - 1)), _id, _tt) {}

    /*
     * Returns the first i in [0, S] such that comp(this(0, i))
     * evaluates to true. Returns -1 if no such i exists.
     * Requires that comp(this(0, i)) is non-decreasing in i.
     */
    template<typename C> int lower_bound(C comp) const {
        if (!comp(this->table[1])) return -1;
        if (comp(T{})) return 0;

        int loc = 1;
        for (T cur{}; loc < this->SZ; ) {
            T mid = this->tt(cur, this->table[2 * loc]);
            if (comp(mid)) {
                loc = 2 * loc;
            } else {
                cur = mid;
                loc = 2 * loc + 1;
            }
        }
        return loc - this->SZ + 1;
    }
};
// }}}

int main() {
    setIO();

    int N; string s; re(N, s);
    suffix_array sa(s);

    auto pp = [](pii a, pii b){ return pii(min(a.f, b.f), max(a.s, b.s)); };
    segment_tree st(N, pii{INT_MAX, INT_MIN}, pp);
    st.set_leaves([&](int i) { return pii{sa.at_rank[i], sa.at_rank[i]}; });

    int ans = 0;
    F0R (i, N) {
        int lo = 1, hi = N - i;
        while (lo <= hi) {
            int mi = (lo + hi) / 2;
            pii r = sa.find_range(i, mi);
            pii o = st(r.f, r.s + 1);
            if (o.f + mi <= i || i + mi <= o.s) {
                ckmax(ans, mi);
                lo = mi + 1;
            } else hi = mi - 1;
        }
    }
    ps(ans);

    return 0;
}



Compiler output:
a.cc:134:21: error: reference to 'monostate' is ambiguous
  134 | template<typename W=monostate> struct wedge {
      |                     ^~~~~~~~~
In file included from /usr/include/x86_64-linux-gnu/c++/14/bits/stdc++.h:80,
                 from a.cc:1:
/usr/include/c++/14/variant:1237:10: note: candidates are: 'struct std::monostate'
 1237 |   struct monostate { };
      |          ^~~~~~~~~
a.cc:129:8: note:                 'struct monostate'
  129 | struct monostate {
      |        ^~~~~~~~~