Submission #1065590

#	Time	Username	Problem	Language	Result	Execution time	Memory
1065590		Flan312	Lampice (COCI19_lampice)	C++17	110 / 110	2599 ms	12196 KiB

lampice

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#define ll long long
#define ld long double
#define eb emplace_back
#define task ""
#define fast ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define nx freopen (task".inp","r",stdin), freopen (task".out","w",stdout);
#define fi first
#define se second
#define pii pair <int, int>
#define tii tuple <int, int, int>
#define all(s) s.begin(), s.end()
using namespace std;
using namespace __gnu_pbds;

const ll base = 311;
const int nmax = 5e4 + 2;

ll pw[nmax];
int n;
string a;
basic_string <int> adj[nmax];
gp_hash_table <ll, bool> mp;

struct Hash
{
    ll hl[nmax], hr[nmax], pw[nmax];
    int len;

    void push_back(char c)
    {
        hl[len + 1] = hl[len] * base + c;
        hr[len + 1] = hr[len] + c * pw[len];
        ++len;
    }

    void pop_back()
    {
        --len;
    }

    void clear()
    {
        len = 0;
    }

    bool isPalin(int l)
    {
        return hl[l] == hr[l];
    }

    ll get(int l)
    {
        return hl[len] - hl[len - l] * pw[l];
    }

    Hash()
    {
        len = 0;
        pw[0] = 1;
        for (int i = 1; i < nmax; ++i)
            pw[i] = pw[i - 1] * base;
        
    }
} hs;

struct centroidDecomposition
{
    int sz[nmax];
    bool del[nmax];

    void init()
    {
        memset(del, 0, (n + 1) * sizeof(bool));
    }

    void dfs(int u, int p)
    {
        sz[u] = 1;
        for (auto &v : adj[u])
        {
            if (v == p || del[v]) continue;
            dfs(v, u);
            sz[u] += sz[v];
        }
    }

    int findCentroid(int u, int p, int total)
    {
        for (auto &v : adj[u])
        {
            if (v == p || del[v]) continue;
            if (sz[v] > (total >> 1))
                return findCentroid(v, u, total);
        }
        return u;
    }

    bool dfs_update(int u, int p, int depth, int len)
    {
        hs.push_back(a[u]);
        if (depth * 2 >= len && hs.isPalin(2 * depth - len)) //duong di qua goc tu 2 dinh con cach goc 1 khoang depth
            mp[hs.get(len - depth)] = 1; 
        if (depth == len && hs.isPalin(len))
            return 1;
        for (auto &v : adj[u])
        {
            if (v == p || del[v]) continue;
            if (dfs_update(v, u, depth + 1, len)) return 1;
        }
        hs.pop_back();
        return 0;
    }

    bool dfs_search(int u, int p, int depth, int len)
    {
        hs.push_back(a[u]);
        if (depth * 2 <= len && mp[hs.get(depth)]) //chi 1 nhanh
            return 1;
        if (depth == len && hs.isPalin(len))
            return 1;
        for (auto &v : adj[u])
        {
            if (v == p || del[v]) continue;
            if (dfs_search(v, u, depth + 1, len)) return 1;
        }
        hs.pop_back();
        return 0;
    }

    bool build(int u, int len)
    {
        dfs(u, -1);
        int centroid = findCentroid(u, -1, sz[u]);
        del[centroid] = 1;

        for (int turn = 0; turn <= 1; ++turn)
        {
            mp.clear();
            for (auto &v : adj[centroid])
            {
                if (del[v]) continue;
                
                hs.clear();
                if (dfs_search(v, centroid, 1, len)) 
                    return 1;
            
                hs.clear();
                hs.push_back(a[centroid]);
                if (dfs_update(v, centroid, 2, len)) 
                    return 1;
            }

            reverse(all(adj[centroid]));
        }

        for (auto &v : adj[centroid])
        {
            if (del[v]) continue;
            if (build(v, len)) return 1;
        }

        return 0;
    }
} cd;

bool check(int mid)
{
    cd.init();
    return cd.build(1, mid);
}

int main()
{
    if (ifstream(task".inp")) nx
    fast

    cin >> n >> a;
    a = ' ' + a;

    for (int u, v, i = 1; i < n; ++i)
    {
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

    int l = 1, r = (n >> 1), ans = 1;
    while(l <= r)
    {
        int mid = l + r >> 1;
        if (check(2 * mid))
        {
            ans = max(ans, 2 * mid);
            l = mid + 1;
        }
        else r = mid - 1;
    }

    l = 1, r = (n >> 1);
    while(l <= r)
    {
        int mid = l + r >> 1;
        if (check(2 * mid + 1))
        {
            ans = max(ans, 2 * mid + 1);
            l = mid + 1;
        }
        else r = mid - 1;
    }
    cout << ans;
}

Compilation message (stderr)

lampice.cpp: In function 'int main()':
lampice.cpp:192:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  192 |         int mid = l + r >> 1;
      |                   ~~^~~
lampice.cpp:204:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  204 |         int mid = l + r >> 1;
      |                   ~~^~~
lampice.cpp:8:20: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 | #define nx freopen (task".inp","r",stdin), freopen (task".out","w",stdout);
      |            ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:176:31: note: in expansion of macro 'nx'
  176 |     if (ifstream(task".inp")) nx
      |                               ^~
lampice.cpp:8:52: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
    8 | #define nx freopen (task".inp","r",stdin), freopen (task".out","w",stdout);
      |                                            ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:176:31: note: in expansion of macro 'nx'
  176 |     if (ifstream(task".inp")) nx
      |                               ^~

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