oj.uz

Submission #499000

# Submission time Handle Problem Language Result Execution time Memory
499000 2021-12-27T02:53:09 Z hoanghq2004 Lampice (COCI19_lampice) C++14
110 / 110
 4663 ms 13076 KB 
#include <bits/stdc++.h>
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")

using namespace std;

const int N = 5e4 + 10;
const int mod = 1e9 + 7;
const int base = 29;

int n;
char c[N];
int big[N], sz[N], del[N];
vector <int> g[N];

void dfs(int u, int p) {
    big[u] = 0, sz[u] = 1;
    for (auto v: g[u]) {
        if (v == p || del[v]) continue;
        dfs(v, u);
        sz[u] += sz[v];
        if (sz[v] > sz[big[u]]) big[u] = v;
    }
}

int centroid(int u) {
    int num = sz[u] / 2;
    while (sz[big[u]] > num) u = big[u];
    return u;
}

// 2len + 2

int H[N], power[N];
int rH[N];

int get_hash(int L, int R) {
    return (0LL + H[R] - 1LL * H[L - 1] * power[R - L + 1] + 1LL * mod * mod) % mod;
}

int check(int u, int len) {
    dfs(u, 0);
    u = centroid(u);
    del[u] = 1;
//    cout << u << ' ' << len << '\n';
    H[1] = c[u] - 'a' + 1;
    unordered_set <int> s;
    function <void(int, int, int)> add = [&](int u, int p, int d) {
        if (d > len) return;
//        cout << "add: " << u << ' ' << p << ' ' << d << '\n';
        H[d] = (1LL * H[d - 1] * base + c[u] - 'a' + 1) % mod;
        s.insert(H[d]);
//        if (u == 3) cout << H[d] << "aa\n";
        for (auto v: g[u]) {
            if (v == p || del[v]) continue;
            add(v, u, d + 1);
        }
    };
    rH[1] = c[u] - 'a' + 1;
    s.insert(H[1]);
    int ok = 0;
    function <void(int, int, int)> calc = [&](int u, int p, int d) {
        if (d > len || ok) return;
        H[d] = (1LL * H[d - 1] * base + c[u] - 'a' + 1) % mod;
        int rem = len - d + 1;
        rH[d] = (1LL * power[d - 1] * (c[u] - 'a' + 1) + rH[d - 1]) % mod;
        // len - d + 1 ... d - (len - d + 1) + 1 ... len - d + 1
        // 2 * d - len
        if (d * 2 - len > 0 && rH[d * 2 - len] == H[d * 2 - len]) {
            if (s.find(get_hash(d * 2 - len, d)) != s.end()) {
                ok = 1;
                return;
            }
        }
        for (auto v: g[u]) {
            if (v == p || del[v]) continue;
            calc(v, u, d + 1);
        }
    };
    for (auto v: g[u]) {
        if (del[v]) continue;
        calc(v, u, 2);
        if (ok) return 1;
        add(v, u, 2);
    }
    s.clear();
    reverse(g[u].begin(), g[u].end());
    for (auto v: g[u]) {
        if (del[v]) continue;
        calc(v, u, 2);
        if (ok) return 1;
        add(v, u, 2);
    }
    for (auto v: g[u]) {
        if (del[v]) continue;
        if (check(v, len)) return 1;
    }
    return 0;
}

int main() {
    ios :: sync_with_stdio(0); cin.tie(0);
    cin >> n;
    for (int i = 1; i <= n; ++i) cin >> c[i];
    power[0] = 1;
    for (int i = 1; i <= n; ++i) power[i] = 1LL * power[i - 1] * base % mod;
    for (int i = 1; i < n; ++i) {
        int u, v;
        cin >> u >> v;
        g[u].push_back(v);
        g[v].push_back(u);
    }
//    cout << check(1, 3);
    int ans = 0;
    int L = 0, R = n / 2;
    while (R - L > 1) {
        int mid = L + R >> 1;
        memset(del, 0, sizeof(del));
        if (check(1, mid * 2)) L = mid;
        else R = mid;
    }
    memset(del, 0, sizeof(del));
    if (check(1, R * 2)) ans = R * 2;
    else ans = L * 2;
    if (!ans) ans = 1;
    L = 1, R = n / 2 + 1;
    while (R - L > 1) {
        int mid = L + R >> 1;
        memset(del, 0, sizeof(del));
        if (check(1, mid * 2 - 1)) L = mid;
        else R = mid;
    }
    memset(del, 0, sizeof(del));
    if (check(1, R * 2 - 1)) ans = max(ans, R * 2 - 1);
    else ans = max(ans, L * 2 - 1);
    cout << ans;
}

Compilation message

lampice.cpp:3: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    3 | #pragma GCC optimization ("O3")
      | 
lampice.cpp:4: warning: ignoring '#pragma GCC optimization' [-Wunknown-pragmas]
    4 | #pragma GCC optimization ("unroll-loops")
      | 
lampice.cpp: In lambda function:
lampice.cpp:66:13: warning: unused variable 'rem' [-Wunused-variable]
   66 |         int rem = len - d + 1;
      |             ^~~
lampice.cpp: In function 'int main()':
lampice.cpp:118:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  118 |         int mid = L + R >> 1;
      |                   ~~^~~
lampice.cpp:129:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  129 |         int mid = L + R >> 1;
      |                   ~~^~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 1744 KB Output is correct
2 Correct 14 ms 1788 KB Output is correct
3 Correct 52 ms 1900 KB Output is correct
4 Correct 59 ms 1892 KB Output is correct
5 Correct 2 ms 1616 KB Output is correct
6 Correct 2 ms 1616 KB Output is correct
7 Correct 1 ms 1616 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 2401 ms 11728 KB Output is correct
2 Correct 2388 ms 11960 KB Output is correct
3 Correct 1843 ms 12180 KB Output is correct
4 Correct 2219 ms 12624 KB Output is correct
5 Correct 2927 ms 13076 KB Output is correct
6 Correct 274 ms 10696 KB Output is correct

Subtask #3
31.0 / 31.0

# Verdict Execution time Memory Grader output
1 Correct 4075 ms 9288 KB Output is correct
2 Correct 4663 ms 8724 KB Output is correct
3 Correct 4339 ms 9308 KB Output is correct
4 Correct 4109 ms 7820 KB Output is correct
5 Correct 3346 ms 8072 KB Output is correct
6 Correct 3212 ms 7500 KB Output is correct

Subtask #4
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 5 ms 1744 KB Output is correct
2 Correct 14 ms 1788 KB Output is correct
3 Correct 52 ms 1900 KB Output is correct
4 Correct 59 ms 1892 KB Output is correct
5 Correct 2 ms 1616 KB Output is correct
6 Correct 2 ms 1616 KB Output is correct
7 Correct 1 ms 1616 KB Output is correct
8 Correct 2401 ms 11728 KB Output is correct
9 Correct 2388 ms 11960 KB Output is correct
10 Correct 1843 ms 12180 KB Output is correct
11 Correct 2219 ms 12624 KB Output is correct
12 Correct 2927 ms 13076 KB Output is correct
13 Correct 274 ms 10696 KB Output is correct
14 Correct 4075 ms 9288 KB Output is correct
15 Correct 4663 ms 8724 KB Output is correct
16 Correct 4339 ms 9308 KB Output is correct
17 Correct 4109 ms 7820 KB Output is correct
18 Correct 3346 ms 8072 KB Output is correct
19 Correct 3212 ms 7500 KB Output is correct
20 Correct 2320 ms 5620 KB Output is correct
21 Correct 2756 ms 6868 KB Output is correct
22 Correct 3880 ms 8388 KB Output is correct
23 Correct 968 ms 4680 KB Output is correct
24 Correct 3248 ms 7112 KB Output is correct
25 Correct 3045 ms 6240 KB Output is correct
26 Correct 4113 ms 8680 KB Output is correct
27 Correct 4141 ms 8952 KB Output is correct
28 Correct 2538 ms 4816 KB Output is correct
29 Correct 2672 ms 4800 KB Output is correct
30 Correct 3049 ms 7312 KB Output is correct
31 Correct 2859 ms 5616 KB Output is correct
32 Correct 2500 ms 8928 KB Output is correct
33 Correct 2231 ms 7048 KB Output is correct