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Submission #676295

# Submission time Handle Problem Language Result Execution time Memory
676295 2022-12-30T08:18:20 Z vuavisao Lampice (COCI19_lampice) C++14
110 / 110
 4365 ms 12184 KB 
#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
using namespace std;

template<typename Lhs, typename Rhs> inline void Max_self(Lhs &a, Rhs b) { a = (a > b ? a : b); }
template<typename Lhs, typename Rhs> inline void Min_self(Lhs &a, Rhs b) { a = (a < b ? a : b); }

const int N = 5e4 + 10;
const int MOD = 1e9 + 7;
const int BASE = 128;

int n;
string s;
vector<int> g[N];

int cnt_node, child[N];
bool rem[N];

int cap;
int pw[N], up[N], down[N];
vector<int> odd, even;

int res = 1;

void dfs_child(int u, int p) {
    ++ cnt_node;
    child[u] = 1;
    for(const auto& v : g[u]) {
        if(v == p || rem[v]) continue;
        dfs_child(v, u);
        child[u] += child[v];
    }
}

int dfs_centroid(int u, int p) {
    for(const auto& v : g[u]) {
        if(v == p || rem[v]) continue;
        if(child[v] > cnt_node / 2) return dfs_centroid(v, u);
    }
    return u;
}

int get_hash(int l, int r) {
    if(l == 0) return down[r];
    return (0ll + down[r] - 1ll * down[l - 1] * pw[r - l + 1] + 1ll * MOD * MOD) % MOD;
}

bool split(int u, int p) {
    cnt_node = 0; dfs_child(u, p);
    u = dfs_centroid(u, p);
    rem[u] = true;

    down[0] = up[0] = s[u] - 'a' + 1;
    unordered_set<int> stt = {};
    function<void(int, int, int)> add = [&] (int u, int p, int len) {
        if(len + 1 > cap) return;
        down[len] = (1ll * down[len - 1] * BASE + s[u] - 'a' + 1) % MOD;
        stt.insert(down[len]);
        for(const auto& v : g[u]) {
            if(v == p || rem[v]) continue;
            add(v, u, len + 1);
        }
    };

    bool have = false;
    function<void(int, int, int)> calc = [&] (int u, int p, int len) {
        if(have || len + 1 > cap) return;
        down[len] = (1ll * down[len - 1] * BASE + s[u] - 'a' + 1) % MOD;
        up[len] = (1ll * up[len - 1] + 1ll * (s[u] - 'a' + 1) * pw[len]) % MOD;
        if(len + 1 == cap) {
            if(up[len] == down[len]) {
                have = true;
                return;
            }
        }
        if(2 * (len + 1) > cap) {
            int use_palin = 2 * (len + 1) - cap - 1;
            if(down[use_palin] == up[use_palin]) {
                int hash = get_hash(use_palin, len);
                if(stt.find(hash) != stt.end()) {
                    have = true;
                    return;
                }
            }
        }
        for(const auto& v : g[u]) {
            if(v == p || rem[v]) continue;
            calc(v, u, len + 1);
        }
    };

    for(const auto& v : g[u]) {
        if(rem[v]) continue;
        calc(v, u, 1);
        if(have) return true;
        add(v, u, 1);
    }

    stt.clear();
    reverse(g[u].begin(), g[u].end());

    for(const auto& v : g[u]) {
        if(rem[v]) continue;
        calc(v, u, 1);
        if(have) return true;
        add(v, u, 1);
    }

    for(const auto& v : g[u]) {
        if(rem[v]) continue;
        if(split(v, u)) return true;
    }
    return false;
}

void solve(bool ODD) {
    const auto& s = (ODD ? odd : even);
    int l = 0, r = (int) s.size() - 1;
    while(l <= r) {
        int mid = (l + r) >> 1;
        cap = s[mid];
        memset(rem, false, sizeof(rem));
        if(split(1, 0)) {
            Max_self(res, cap);
            l = mid + 1;
        }
        else {
            r = mid - 1;
        }
    }
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen("COCI19_lampice.inp", "r")) {
        freopen("COCI19_lampice.inp", "r", stdin);
        freopen("COCI19_lampice.out", "w", stdout);
    }
    cin >> n >> s; s = ' ' + s;
    for(int i = 2; i <= n; ++ i) {
        int u, v; cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
    pw[0] = 1;
    for(int i = 1; i <= n; ++ i) {
        pw[i] = 1ll * pw[i - 1] * BASE % MOD;
        if(i & 1) {
            if(i > 1) {
                odd.push_back(i);
            }
        }
        else {
            even.push_back(i);
        }
    }
    solve(0); solve(1);
    cout << res;
    return 0;
}

/// Code by vuavisao

Compilation message

lampice.cpp: In function 'int32_t main()':
lampice.cpp:140:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  140 |         freopen("COCI19_lampice.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
lampice.cpp:141:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  141 |         freopen("COCI19_lampice.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 1492 KB Output is correct
2 Correct 11 ms 1620 KB Output is correct
3 Correct 42 ms 1772 KB Output is correct
4 Correct 46 ms 1744 KB Output is correct
5 Correct 1 ms 1492 KB Output is correct
6 Correct 1 ms 1492 KB Output is correct
7 Correct 1 ms 1492 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 2068 ms 10928 KB Output is correct
2 Correct 2073 ms 11148 KB Output is correct
3 Correct 1347 ms 11352 KB Output is correct
4 Correct 1658 ms 11792 KB Output is correct
5 Correct 2512 ms 12184 KB Output is correct
6 Correct 163 ms 9036 KB Output is correct

Subtask #3
31.0 / 31.0

# Verdict Execution time Memory Grader output
1 Correct 3456 ms 8852 KB Output is correct
2 Correct 4365 ms 8588 KB Output is correct
3 Correct 3794 ms 8968 KB Output is correct
4 Correct 3727 ms 7776 KB Output is correct
5 Correct 3066 ms 7696 KB Output is correct
6 Correct 2895 ms 7252 KB Output is correct

Subtask #4
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 4 ms 1492 KB Output is correct
2 Correct 11 ms 1620 KB Output is correct
3 Correct 42 ms 1772 KB Output is correct
4 Correct 46 ms 1744 KB Output is correct
5 Correct 1 ms 1492 KB Output is correct
6 Correct 1 ms 1492 KB Output is correct
7 Correct 1 ms 1492 KB Output is correct
8 Correct 2068 ms 10928 KB Output is correct
9 Correct 2073 ms 11148 KB Output is correct
10 Correct 1347 ms 11352 KB Output is correct
11 Correct 1658 ms 11792 KB Output is correct
12 Correct 2512 ms 12184 KB Output is correct
13 Correct 163 ms 9036 KB Output is correct
14 Correct 3456 ms 8852 KB Output is correct
15 Correct 4365 ms 8588 KB Output is correct
16 Correct 3794 ms 8968 KB Output is correct
17 Correct 3727 ms 7776 KB Output is correct
18 Correct 3066 ms 7696 KB Output is correct
19 Correct 2895 ms 7252 KB Output is correct
20 Correct 2108 ms 5732 KB Output is correct
21 Correct 2502 ms 6696 KB Output is correct
22 Correct 3581 ms 8316 KB Output is correct
23 Correct 655 ms 4552 KB Output is correct
24 Correct 2872 ms 6708 KB Output is correct
25 Correct 2625 ms 5960 KB Output is correct
26 Correct 3677 ms 8764 KB Output is correct
27 Correct 3877 ms 8628 KB Output is correct
28 Correct 2126 ms 4500 KB Output is correct
29 Correct 2198 ms 4776 KB Output is correct
30 Correct 2592 ms 6984 KB Output is correct
31 Correct 2504 ms 5476 KB Output is correct
32 Correct 2095 ms 8488 KB Output is correct
33 Correct 1903 ms 6968 KB Output is correct