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Submission #501007

# Submission time Handle Problem Language Result Execution time Memory
501007 2022-01-02T06:25:24 Z Duy_e Lampice (COCI19_lampice) C++14
110 / 110
 3821 ms 30752 KB 
#include <bits/stdc++.h>
#define debug cout << "fuck\n";
#define ll long long
#define ull unsigned long long
#define pii pair<long long, long long>
#define st first
#define nd second
#define file "test"
using namespace std;
const long long oo = 1e18;
const long long N = 2e5 + 5;
const long long base = 311;
const long long MOD = 2e9 + 7;

ll H[N], rH[N], pw[N], h[N], up[20][N];

vector <int> d[N], centroid;
string SS;

int n, numchild[N], s[N];
bool dead[N];

// find centroid
int get_size(int p, int u) {
    int ans = 1;
    for (int v: d[u]) if (v != p && !dead[v]) 
        ans += get_size(u, v);
    return ans;
}

int find_centroid(int S, int p, int u, int ma = 0) {
    numchild[u] = 1;
    for (int v: d[u]) if (v != p && !dead[v]) {
        int get = find_centroid(S, u, v);

        if (get != -1) return get;

        numchild[u] += numchild[v];
        ma = max(ma, numchild[v]);
    }

    ma = max(ma, S - numchild[u]);

    return ma <= S/2 ? u: -1;
}

void FIND_CENTROID() { 
    queue <int> q; q.push(1);
    while (q.size()) {
        int u = q.front(); q.pop();
        dead[u = find_centroid(get_size(0, u), 0, u)] = true;
        centroid.push_back(u); 
        for (int v: d[u]) if (!dead[v]) q.push(v); 
    }
}

vector <int> save[N];

void dfs(int p, int u, int vi) {
    for (int v: d[u]) if (v != p && !dead[v]) {
        h[v] = h[u] + 1;
        H[v] = (H[u]*base + s[v]) % MOD;
        rH[v] = (rH[u] + pw[h[v]]*s[v]) % MOD;

        up[0][v] = u;
        for (int i = 1; (1 << i) <= h[v]; i ++)
            up[i][v] = up[i - 1][up[i - 1][v]];

        save[vi == 0 ? v : vi].push_back(v);
        dfs(u, v, vi == 0 ? v : vi);
    }
}   

int kanc(int k, int u) {
    int x = u;
    for (int i = 19; i >= 0; i --) 
        if (k & 1 << i) u = up[i][u];
    return u;
}

ll get(int u, int v) {return (H[v] - H[u] * pw[h[v] - h[u]] + MOD * MOD) % MOD;}

bool solve_len(int len, int u) {
    // return true;

    if (len <= 1) return true;
    H[u] = s[u]; rH[u] = s[u]; h[u] = 0;
    dfs(u, u, 0);

    unordered_set <int> st, st2; st.insert(0); st2.insert(0);

    // cout << "--------- " << u << " ----------\n";
    for (int vi: d[u]) if (!dead[vi]) {
        for (int v: save[vi]) {
            // cout << v << ' ';
            int mis = len - h[v] - 1; if (mis < 0) continue;
            // cout << u << ' ' << v << ' ' << get(u, v) << '\n';
            if (mis >= h[v]) {
                if (st2.count(get(u, v))) return true;
            } else {
                int anc = kanc(mis, v);
                if (H[anc] == rH[anc] && st.count(get(anc, v))) return true;
            }
        }
        // cout << '\n';
        for (int v: save[vi]) {
            int mis = len - h[v] - 1; if (mis < 0) continue;
            if (mis > h[v]) st.insert(get(u, v)); else  {
                int anc = kanc(mis, v);
                if (H[anc] == rH[anc]) st2.insert(get(anc, v));
            }
        }
    }

    return false;
}


int solve(int len) {
    for (int i = 1; i <= n; i ++) dead[i] = false;
    for (int u: centroid) {
        int tmp = solve_len(len, u);
        dead[u] = true;
        for (int v: d[u]) save[v].clear();
        if (tmp) return true;
    }

    return false;
}

int bs(int x) {
    int l = 0, r = n/2 + 1, ans = x;
    while (l <= r) {
        int mid = l + r >> 1;
        // cout << mid*2 + x << '\n';
        if (solve(2*mid + x))
            ans = mid * 2 + x, l = mid + 1;
        else
            r = mid - 1;
    }

    return ans;
}

ll SOLVE_CENTROID() {   
    return max(bs(0), bs(1));
}   

int main()
{
    ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
    // #ifndef ONLINE_JUDGE
    //     freopen(file".inp","r",stdin); freopen(file".out","w",stdout);
    // #endif
    
    cin >> n >> SS;
    // s = ' ' + s;

    for (int i = 1; i <= n; i ++)
        s[i] = SS[i - 1] - 'a' + 1;

    pw[0] = 1;
    for (int i = 1; i < N; i ++) 
        pw[i] = pw[i - 1]*base % MOD;

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

    FIND_CENTROID();
    cout << SOLVE_CENTROID();// << ' ' << 1;
    return 0;
}    
/**  /\_/\
    (= ._.)
    / >🍵 \>🍮
  ________________________
 / Brainstorming section /
/=======================/
---
===
g++ -O2 -std=c++11 -Wall -Wl,--stack=268435456 somerandomthings.cpp -o somerandomthings.exe
12780

===
**/
// Before submit: spot the visible bug by reading the code.

Compilation message

lampice.cpp: In function 'int kanc(int, int)':
lampice.cpp:75:9: warning: unused variable 'x' [-Wunused-variable]
   75 |     int x = u;
      |         ^
lampice.cpp: In function 'int bs(int)':
lampice.cpp:134:21: warning: suggest parentheses around '+' inside '>>' [-Wparentheses]
  134 |         int mid = l + r >> 1;
      |                   ~~^~~

Subtask #1
17.0 / 17.0

# Verdict Execution time Memory Grader output
1 Correct 9 ms 11388 KB Output is correct
2 Correct 13 ms 11480 KB Output is correct
3 Correct 32 ms 11596 KB Output is correct
4 Correct 34 ms 11776 KB Output is correct
5 Correct 7 ms 11264 KB Output is correct
6 Correct 7 ms 11212 KB Output is correct
7 Correct 7 ms 11212 KB Output is correct

Subtask #2
25.0 / 25.0

# Verdict Execution time Memory Grader output
1 Correct 1582 ms 27940 KB Output is correct
2 Correct 1396 ms 28296 KB Output is correct
3 Correct 1037 ms 29904 KB Output is correct
4 Correct 1033 ms 30752 KB Output is correct
5 Correct 1707 ms 30416 KB Output is correct
6 Correct 358 ms 30136 KB Output is correct

Subtask #3
31.0 / 31.0

# Verdict Execution time Memory Grader output
1 Correct 3821 ms 27420 KB Output is correct
2 Correct 3074 ms 26976 KB Output is correct
3 Correct 2995 ms 26964 KB Output is correct
4 Correct 3340 ms 26548 KB Output is correct
5 Correct 2323 ms 25692 KB Output is correct
6 Correct 2404 ms 24008 KB Output is correct

Subtask #4
37.0 / 37.0

# Verdict Execution time Memory Grader output
1 Correct 9 ms 11388 KB Output is correct
2 Correct 13 ms 11480 KB Output is correct
3 Correct 32 ms 11596 KB Output is correct
4 Correct 34 ms 11776 KB Output is correct
5 Correct 7 ms 11264 KB Output is correct
6 Correct 7 ms 11212 KB Output is correct
7 Correct 7 ms 11212 KB Output is correct
8 Correct 1582 ms 27940 KB Output is correct
9 Correct 1396 ms 28296 KB Output is correct
10 Correct 1037 ms 29904 KB Output is correct
11 Correct 1033 ms 30752 KB Output is correct
12 Correct 1707 ms 30416 KB Output is correct
13 Correct 358 ms 30136 KB Output is correct
14 Correct 3821 ms 27420 KB Output is correct
15 Correct 3074 ms 26976 KB Output is correct
16 Correct 2995 ms 26964 KB Output is correct
17 Correct 3340 ms 26548 KB Output is correct
18 Correct 2323 ms 25692 KB Output is correct
19 Correct 2404 ms 24008 KB Output is correct
20 Correct 1362 ms 19740 KB Output is correct
21 Correct 1677 ms 20544 KB Output is correct
22 Correct 2391 ms 24580 KB Output is correct
23 Correct 641 ms 18804 KB Output is correct
24 Correct 2346 ms 25176 KB Output is correct
25 Correct 2259 ms 24848 KB Output is correct
26 Correct 2929 ms 27060 KB Output is correct
27 Correct 3310 ms 25704 KB Output is correct
28 Correct 1676 ms 22836 KB Output is correct
29 Correct 1944 ms 23052 KB Output is correct
30 Correct 2394 ms 26496 KB Output is correct
31 Correct 2142 ms 24556 KB Output is correct
32 Correct 2120 ms 27576 KB Output is correct
33 Correct 1469 ms 22912 KB Output is correct