Submission #1037118

#	Time	Username	Problem	Language	Result	Execution time	Memory
1037118		TrinhKhanhDung	Lampice (COCI19_lampice)	C++14	110 / 110	3120 ms	12772 KiB

lampice

#include <bits/stdc++.h>
#define ll long long
#define fi first
#define se second
#define sz(x) (int)x.size()
#define ALL(v) v.begin(),v.end()
#define MASK(k) (1LL << (k))
#define BIT(x, i) (((x) >> (i)) & 1)
#define oo (ll)1e18
#define INF (ll)1e9
#define MOD (ll)(1e9 + 7)

using namespace std;

template<class T1, class T2>
    bool maximize(T1 &a, T2 b){if(a < b){a = b; return true;} return false;}

template<class T1, class T2>
    bool minimize(T1 &a, T2 b){if(a > b){a = b; return true;} return false;}

template<class T1, class T2>
    void add(T1 &a, T2 b){a += b; if(a >= MOD) a -= MOD;}

template<class T1, class T2>
    void sub(T1 &a, T2 b){a -= b; if(a < 0) a += MOD;}

template<class T>
    void cps(T &v){sort(ALL(v)); v.resize(unique(ALL(v)) - v.begin());}

const int MAX = 5e4 + 10;
const int base = 311;

int N;
string s;
vector<int> adj[MAX];
int nChild[MAX], pw[MAX], height[MAX];
bool ok[MAX];
int ans = 0;
bool isDel[MAX];

void input(){
    cin >> N;
    cin >> s;
    s = "0" + s;
    for(int i=1; i<N; i++){
        int u, v;
        cin >> u >> v;
        adj[u].push_back(v);
        adj[v].push_back(u);
    }

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

namespace subtask1{
    void dfs(int u, int p, int down, int up, int height){
        down = (1LL * down * base + s[u]) % MOD;
        up = (1LL * up + 1LL * s[u] * pw[height] % MOD) % MOD;
        if(down == up) maximize(ans, height + 1);

        for(int v: adj[u]) if(v != p){
            dfs(v, u, down, up, height + 1);
        }
    }

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

        for(int i=1; i<=N; i++){
            dfs(i, 0, 0, 0, 0);
        }
        cout << ans << '\n';
    }
}

void countChild(int u, int p){
    nChild[u] = 1;
    for(int v: adj[u]) if(v != p && !isDel[v]){
        countChild(v, u);
        nChild[u] += nChild[v];
    }
}

int centroid(int u, int p, int n){
    for(int v: adj[u]) if(v != p && !isDel[v]){
        if(nChild[v] * 2 > n) return centroid(v, u, n);
    }
    return u;
}

bool calc(int u, int p, int h, int down, int up, int len, unordered_map<int, int> &om){
    h++;
    down = (1LL * down * base + s[u]) % MOD;
    up = (1LL * up + 1LL * s[u] * pw[h] % MOD) % MOD;

    if(h + 1 > len) return false;
//    cout << u << ' ' << h << ' ' << down << ' ' << up << '\n';
    height[h + 1] = down;

    if((h + 1) * 2 >= len){
        int par = 2 * (h + 1) - len;
        if(ok[par] && om.count((height[h + 1] - 1LL * height[par] * pw[h + 1 - par] % MOD + MOD * MOD) % MOD)){
            return true;
        }
    }

    if(down == up) ok[h + 1] = true;
    bool ans = false;
    for(int v: adj[u]) if(v != p && !isDel[v]){
        ans = ans || calc(v, u, h, down, up, len, om);
    }

    ok[h + 1] = false;

    return ans;
}

void update(int u, int p, int h, int down, int up, int len, unordered_map<int, int> &om){
    h++;
    down = (1LL * down * base + s[u]) % MOD;
    up = (1LL * up + 1LL * s[u] * pw[h] % MOD) % MOD;
    if(h + 1 > len) return;

    om[down] = true;
    for(int v: adj[u]) if(v != p && !isDel[v]){
        update(v, u, h, down, up, len, om);
    }
}

bool solve(int a, int len){
    countChild(a, 0);
    int u = centroid(a, 0, nChild[a]);
//    cout << u << '\n';

    unordered_map<int, int> om;
    om[s[u]] = true;

    for(int v: adj[u]) if(!isDel[v]){
        ok[0] = true;
        height[0] = 0;
        if(calc(v, u, -1, 0, 0, len, om)) return true;
        update(v, u, 0, s[u], s[u], len, om);
    }

    om.clear();
    reverse(ALL(adj[u]));
    for(int v: adj[u]) if(!isDel[v]){
        ok[0] = ok[1] = true;
        height[0] = 0;
        height[1] = s[u];
        if(calc(v, u, 0, s[u], s[u], len, om)) return true;
        update(v, u, -1, 0, 0, len, om);
    }

    isDel[u] = true;
    for(int v: adj[u]) if(!isDel[v]){
        if(solve(v, len)) return true;
    }

    return false;
}

bool check(int k){
    if(k == 0 || k == 1) return true;

    memset(isDel, false, (N + 3) * sizeof(bool));
    return solve(1, k);
}

int odd(){
    int l = 0, r = N - N / 2;

    while(l < r){
        int m = (l + r) >> 1;
        if((l + r) & 1) m++;
        if(check(m * 2 + 1)){
            l = m;
        }
        else{
            r = m - 1;
        }
    }

    return l * 2 + 1;
}

int even(){
    int l = 0, r = N - N / 2;

    while(l < r){
        int m = (l + r) >> 1;
        if((l + r) & 1) m++;
        if(check(m * 2)){
            l = m;
        }
        else{
            r = m - 1;
        }
    }
    return l * 2;
}

int main(){
    ios_base::sync_with_stdio(0); cin.tie(0);

    input();

    cout << max(odd(), even());

    return 0;
}

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