Submission #1115822

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115822		ljtunas	Lampice (COCI19_lampice)	C++14	110 / 110	1756 ms	90444 KiB

lampice

// author : anhtun_hi , nqg
#include <bits/stdc++.h>
#define ll long long
#define ii pair<ll, ll>
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define reset(h, v)    memset(h, v, sizeof h)
#define Forv(i, a)     for(auto& i : a)
#define For(i, a, b)   for(int i = a; i <= b; ++i)
#define Ford(i, a, b)  for(int i = a; i >= b; --i)
#define c_bit(i)     __builtin_popcountll(i)
#define Bit(mask, i)    ((mask >> i) & 1LL)
#define onbit(mask, i)  ((mask) bitor (1LL << i))
#define offbit(mask, i) ((mask) &~ (1LL << i))
#define TIME (1.0 * clock() / CLOCKS_PER_SEC)
using namespace std;
namespace std {
    template <typename T, int D>
    struct _vector : public vector <_vector <T, D - 1>> {
        static_assert(D >= 1, "Dimension must be positive!");
        template <typename... Args>
        _vector(int n = 0, Args... args) : vector <_vector <T, D - 1>> (n, _vector <T, D - 1> (args...)) {}
    };
    template <typename T> struct _vector <T, 1> : public vector <T> {
        _vector(int n = 0, const T& val = T()) : vector <T> (n, val) {}
    };
    template <class A, class B> bool minimize(A &a, B b){return a > b ? a = b, true : false;}
    template <class A, class B> bool maximize(A &a, B b){return a < b ? a = b, true : false;}
}
const int dx[] = {0, 0, +1, -1}, dy[] = {-1, +1, 0, 0}, LOG = 20, base = 311, inf = 1e9 + 5;
const int MAXN = 1e6 + 5;
const  ll  mod = 1e9 + 7;
const  ll   oo = 1e18;

//#define int long long

int n; vector<int> g[MAXN];
string s;
ll p[MAXN];

int sz[MAXN]; ll h[MAXN]; bool del[MAXN];

void dfsSize(int u, int par){
    sz[u] = 1;
    Forv(v, g[u]) if(v != par && !del[v]) dfsSize(v, u), sz[u] += sz[v];
}

int find(int u, int par, int n){
    Forv(v, g[u]) if(v != par && !del[v] && sz[v] * 2 > n) return find(v, u, n);
    return u;
}

ll mxhigh = 0, mxlen;
ll hashup[MAXN], hashdown[MAXN], a[MAXN];
map<ll, bool> mp[MAXN]; bool op;


vector<int> List;
void add(int u, int par){
    if(op) return;
    h[u] = h[par] + 1;
    if (h[u] + 1 > mxlen) return;
    maximize(mxhigh, h[u]);
    hashup[u] = (hashup[par] * base + s[u] - 'a' + 1) % mod;
    hashdown[u] = (hashdown[par] + p[h[u]] * (s[u] - 'a' + 1)) % mod;
    ll cur = (1LL * p[mxlen - h[u] - 1] * hashdown[u] - hashup[u] + mod) % mod;
    if (mp[mxlen - h[u] - 1].find(cur) != mp[mxlen - h[u] - 1].end()){
        op = true;
        return;
    }
    if (h[u] + 1 == mxlen && hashdown[u] == (hashup[u] + p[h[u]] * (s[u] - 'a' + 1)) % mod){
        op = true;
        return;
    }
    a[u] = cur, List.push_back(u);
    Forv(v, g[u]) if(v != par && !del[v]) add(v, u);
}

void solve(int u, int par){
    if(op) return;
    dfsSize(u, par);
    int centroid = find(u, par, sz[u]);
    del[centroid] = true;
    mxhigh = 0, h[centroid] = 0, hashup[centroid] = 0, hashdown[centroid] = s[centroid] - 'a' + 1;
    Forv(v, g[centroid]) if(v != par && !del[v]){
        add(v, centroid);
        Forv(i, List) mp[h[i]][a[i]] = true;
        List.clear();
    }
    For(i, 0, mxhigh) mp[i].clear();
    Forv(v, g[centroid]) if(v != par && !del[v]) solve(v, centroid);
}

bool check(int val){
    reset(del, 0);
    op = false; mxlen = val;
    solve(1, 0);
    return op;
}

void Solve() {
    cin >> n >> s;
    s = ' ' + s;
    For(i, 1, n - 1){
        int u, v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    p[0] = 1;
    For(i, 1, n) p[i] = p[i - 1] * base % mod;
    int ans = 1;
    For(_, 0, 1){
        int l = 0, r = n / 2 + 1;
        while(r - l > 1){
            int mid = l + r >> 1;
            if(check(mid * 2 + _)) l = mid;
            else r = mid;
        }
        maximize(ans, _ + l * 2);
    }
    cout << ans << '\n';
}

signed main() {
    cin.tie(0) -> sync_with_stdio(0);
    if(fopen("noel.inp", "r")) {
        freopen("noel.inp", "r", stdin);
        freopen("noel.out", "w", stdout);
    }

    int t = 1;
//    cin >> t;
    while(t --) Solve();

    return 0;
}

Compilation message (stderr)

lampice.cpp: In function 'void Solve()':
lampice.cpp:116:25: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  116 |             int mid = l + r >> 1;
      |                       ~~^~~
lampice.cpp: In function 'int main()':
lampice.cpp:128:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  128 |         freopen("noel.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:129:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  129 |         freopen("noel.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 17 / 17
• Subtask 2: 25 / 25
• Subtask 3: 31 / 31
• Subtask 4: 37 / 37