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답안 #640410

# 제출 시각 아이디 문제 언어 결과 실행 시간 메모리
640410 2022-09-14T15:01:15 Z LeonaRaging Lampice (COCI19_lampice) C++14
17 / 110
 5000 ms 14120 KB 
#include <bits/stdc++.h>
using namespace std;

#define fi first
#define se second
#define ll long long
#define pb push_back
#define db(val) "[" #val " = " << (val) << "] "

const ll mod = 1e9 + 7;
const int maxn = 1e5 + 4;
const int INF = 1e9;
const ll base = 31;
const int N = 18;

int n, len, root, used[maxn], h[maxn], spt[maxn][20];
string s;
vector<int> adj[maxn];
ll Pow[maxn], Inv[maxn], up[maxn], down[maxn];
unordered_map<ll,bool> L, cur;
bool flag;

ll add(ll a, ll b) {
    a += b; if (a > mod) a -= mod;
    return a;
}

ll del(ll a, ll b) {
    a -= b; if (a < 0) a += mod;
    return a;
}

void pre(int u, int p) {
    if (p) 
        down[u] = add(down[p], (s[u] - 'a' + 1) * Pow[h[u] - 1]);
    if (p) 
        up[u] = add(up[p] * base % mod, s[u] - 'a' + 1);
    spt[u][0] = p;
    for (int j = 1; j <= N; j++)
        spt[u][j] = spt[spt[u][j - 1]][j - 1];
    for (int v : adj[u])
        if (v != p && !used[v]) {
            h[v] = h[u] + 1;
            pre(v, u);
        }
}

int jump(int u, int k) {
    for (int j = N; j >= 0; j--)
        if (k >> j & 1)
            u = spt[u][j];
    return u;
}

void dfs(int u, int p) {
    if (len < h[u]) return;
    int k = len - h[u] - 1, c = jump(u, k);
    if (c && add(up[c], (s[root] - 'a' + 1) * Pow[h[c]] % mod) == 
            add(down[c] * base % mod, (s[root] - 'a' + 1))) {
        if (k == 0)
            return flag = true, void();
        ll val = del(up[u], up[c] * Pow[k] % mod) ;
        if (L.find(val) != L.end()) {
            return flag = true, void();
        }
    }
    cur[up[u]] = 1;
    for (int v : adj[u])
        if (v != p && !used[v])
            dfs(v, u);
}

void Solve(int c) {
    h[c] = 0;
    up[c] = down[c] = 0;
    pre(c, 0);
    L.clear();
    for (int v : adj[c]) 
        if (!used[v]) {
            dfs(v, c);
            for (auto it : cur)
                L[it.fi] = 1;
            cur.clear();
        }   
    reverse(adj[c].begin(), adj[c].end());
    L.clear();
    for (int v : adj[c]) 
        if (!used[v]) {
            dfs(v, c);
            for (auto it : cur)
                L[it.fi] = 1;
            cur.clear();
        }   
}

struct Centroid_Decomposition {
    int sz[maxn];
    int dfs(int u, int p) {
        sz[u] = 1;
        for (int v : adj[u])
            if (!used[v] && v != p)
                sz[u] += dfs(v, u);
        return sz[u];
    }
    int Centroid(int u, int p, int tot) {
        for (int v : adj[u])
            if (!used[v] && v != p && sz[v] > tot / 2)
                return Centroid(v, u, tot);
        return u;
    }
    void build(int u) {
        int c = Centroid(u, 0, dfs(u, 0));
        root = c;
        Solve(c);
        used[c] = 1;
        for (int v : adj[c])
            if (!used[v])
                build(v);
    }
} Cen;

bool ok(int m, int sign) {
    flag = false;
    memset(used, 0, sizeof used);
    len = 2 * m + sign;
    Cen.build(1);
    return flag;
}

ll Expo(ll a, int b) {
    if (b == 0) return 1;
    ll t = Expo(a, b / 2);
    (t *= t) %= mod;
    if (b & 1) (t *= a) %= mod;
    return t;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    //freopen(".INP", "r", stdin);
    //freopen(".OUT", "w", stdout);
    cin >> n >> s;
    s = ' ' + s;
    for (int i = 1; i < n; i++) {
        int u, v; cin >> u >> v;
        adj[u].pb(v);
        adj[v].pb(u);
    }
    Pow[0] = Inv[0] = 1;
    for (int i = 1; i <= n; i++) {
        Pow[i] = Pow[i - 1] * base % mod;
        Inv[i] = Expo(Pow[i], mod - 2);
    }
    // return cout << ok(4, 1), 0;
    int L = 1, R = n / 2, res = 1;
    while (L <= R) {
        int mid = (L + R) / 2;
        if (ok(mid, 1)) {
            res = 2 * mid + 1;
            L = mid + 1;
        }
        else R = mid - 1;
    }
    L = 1, R = n / 2;
    while (L <= R) {
        int mid = (L + R) / 2;
        if (ok(mid, 0)) {
            res = max(res, 2 * mid);
            L = mid + 1;
        }
        else R = mid - 1;
    }
    cout << res;
}

Subtask #1
17.0 / 17.0

# 결과 실행 시간 메모리 Grader output
1 Correct 12 ms 3156 KB Output is correct
2 Correct 27 ms 3212 KB Output is correct
3 Correct 120 ms 3412 KB Output is correct
4 Correct 152 ms 3448 KB Output is correct
5 Correct 1 ms 2644 KB Output is correct
6 Correct 2 ms 3028 KB Output is correct
7 Correct 2 ms 3028 KB Output is correct

Subtask #2
0 / 25.0

# 결과 실행 시간 메모리 Grader output
1 Execution timed out 5066 ms 14120 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #3
0 / 31.0

# 결과 실행 시간 메모리 Grader output
1 Execution timed out 5039 ms 13872 KB Time limit exceeded
2 Halted 0 ms 0 KB -

Subtask #4
0 / 37.0

# 결과 실행 시간 메모리 Grader output
1 Correct 12 ms 3156 KB Output is correct
2 Correct 27 ms 3212 KB Output is correct
3 Correct 120 ms 3412 KB Output is correct
4 Correct 152 ms 3448 KB Output is correct
5 Correct 1 ms 2644 KB Output is correct
6 Correct 2 ms 3028 KB Output is correct
7 Correct 2 ms 3028 KB Output is correct
8 Execution timed out 5066 ms 14120 KB Time limit exceeded
9 Halted 0 ms 0 KB -