Submission #668125

#	Time	Username	Problem	Language	Result	Execution time	Memory
668125		jeroenodb	Lampice (COCI19_lampice)	C++14	110 / 110	2755 ms	11612 KiB

lampice

#include "bits/stdc++.h"
using namespace std;
#define all(x) begin(x),end(x)
template<typename A, typename B> ostream& operator<<(ostream &os, const pair<A, B> &p) { return os << '(' << p.first << ", " << p.second << ')'; }
template<typename T_container, typename T = typename enable_if<!is_same<T_container, string>::value, typename T_container::value_type>::type> ostream& operator<<(ostream &os, const T_container &v) { string sep; for (const T &x : v) os << sep << x, sep = " "; return os; }
#define debug(a) cerr << "(" << #a << ": " << a << ")\n";
typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int,int> pi;
const int mxN = 5e4+1, oo = 1e9;
const long long MD = 1000001011;
template<long long MOD=MD> struct mdint {
    int d=0;
    mdint () {d=0;}
    mdint (long long _d) : d(_d%MOD){
        if(d<0) d+=MOD;
    };
    friend mdint& operator+=(mdint& a, const mdint& o) {
        a.d+=o.d; if(a.d>=MOD) a.d-=MOD;
        return a;
    }
    friend mdint& operator-=(mdint& a, const mdint& o) {
        a.d-=o.d; if(a.d<0) a.d+=MOD;
        return a;
    }
    friend mdint& operator*=(mdint& a, const mdint& o) {
        return a = mdint((ll)a.d*o.d);
    }
    mdint operator*(const mdint& o) const {
        mdint res = *this;
        res*=o;
        return res;
    }
    mdint operator+(const mdint& o) const {
        mdint res = *this;
        res+=o;
        return res;
    }
    mdint operator-(const mdint& o) const {
        mdint res = *this;
        res-=o;
        return res;
    }
    mdint operator^(long long b) const {
        mdint tmp = 1;
        mdint power = *this;
        while(b) {
            if(b&1) {
                tmp = tmp*power;
            }
            power = power*power;
            b/=2;
        }
        return tmp;
    }
    friend mdint operator/=(mdint& a, const mdint& o) {
        a *= (o^(MOD-2));
        return a;
    }
    mdint operator/(const mdint& o) {
        mdint res = *this;
        res/=o;
        return res;
    }
    bool operator==(const mdint& o) { return d==o.d;}
    bool operator!=(const mdint& o) { return d!=o.d;}
    friend istream& operator>>(istream& c, mdint& a) {return c >> a.d;}
    friend ostream& operator<<(ostream& c, const mdint& a) {return c << a.d;}
};
using  mint = mdint<MD>;
mint pw[mxN];
const mint base = 546575;
void precomp() {
    pw[0]=1;
    for(int i=1;i<mxN;++i) pw[i]=pw[i-1]*base;
}

const int S = 20000019;
struct bloomfilter {
    bitset<S> bs = {};
    vi v;
    bool check(ll i) {
        return bs[i%S] and bs[(i*6755^1244546)%S];
    }
    void clear() {
        for(auto i : v) {
            add(i,0);
        }
        v.clear();
    }
    void add(ll i, bool s=1) {
        if(s) v.push_back(i);
        bs[i%S]=bs[(i*6755^1244546)%S]=s;
    }
} bf[2];

bitset<mxN> vis;
basic_string<int> adj[mxN];
int sz[mxN];
string s;
void dfsz(int at) {
    vis[at]=1;
    sz[at]=1;
    for(int to : adj[at]) if(!vis[to]) {
        dfsz(to);        
        sz[at]+=sz[to];
    }
    vis[at]=0;
}
int LEN;
vector<char> palin = {1};
vector<mint> pref = {0};
int d=1;
bool CHECKING=false;
tuple<bool,bool,int> good() {
    int check = min(d,LEN-d);
    if(d>check) {
        if(!palin[d-check]) return {0,0,0};
    }
    return {true,  d >= (LEN+1 + !CHECKING)/2, (pref.back()- pw[check]*pref[d-check]).d};
}
bool foundLEN=false;
mint b=0;
template<typename F> void dfsD(int at, F func) {
    d++;
    b+=pw[d-1]*s[at];
    pref.push_back(pref.back()*base+s[at]);
    vis[at]=1;
    palin.push_back(pref.back()==b);
    auto [g,big,val] = good();
    if(g) func(val,big);
    for(int to : adj[at]) if(!vis[to]) {
        dfsD(to,func);
    }
    palin.pop_back();
    pref.pop_back();
    vis[at]=0;
    b-=pw[d-1]*s[at];
    d--;
}

int centroid(int at) {
    int total=sz[at], from=-1;
    while(true) {
        bool f=false;
        for(int to : adj[at]) if(to!=from and !vis[to]) {
            if(sz[to]*2>total) {
                from=at;
                at=to;
                f=true;
                break;
            }
        }
        if(!f) return at;
    }
}

bool decomp(int at) {

    dfsz(at);
    int c = centroid(at);
    vis[c]=1;
    for(int to : adj[c]) if(!vis[to]) {
        if(decomp(to)) {
            vis[c]=0;
            return true;
        }
    }
    // now the real work.
    bf[0].add(0);
    for(int to : adj[c]) if(!vis[to]) {
        auto mycheck = [&](int v, bool big) {
            if(bf[!big].check(v)) {
                foundLEN=true;
            }
        };
        auto myadd = [&](int v, bool big) {
            bf[big].add(v);
        };
        d=1;
        palin.push_back(1);
        pref.push_back(s[c]);
        CHECKING=true;
        b=s[c];
        dfsD(to,mycheck);
        palin.pop_back();
        pref.pop_back();
        CHECKING=false;
        d=0;
        b=0;
        dfsD(to,myadd);

        if(foundLEN) break;
    }
    bf[0].clear();
    bf[1].clear();
    vis[c]=0;
    return foundLEN;
}


int main() {
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    precomp();
    int n; cin >> n;
    pref.reserve(n+2);
    palin.reserve(n+2);
    for(auto& b : bf) b.v.reserve(n+2);
    cin >> s;
    for(int i=0;i<n-1;++i) {
        int a,b; cin >> a >> b,--a,--b;
        adj[a].push_back(b);
        adj[b].push_back(a);
    }
    int lo = 0,hi=n/2;
    while(lo<hi) {
        int mid = (lo+hi+1)/2;
        LEN = mid*2;
        foundLEN=0;
        if(decomp(0)) {
            lo = mid;
        } else hi = mid-1;
    }
    int ans=lo*2;
    lo=0,hi = (n-1)/2;
    while(lo<hi) {
        int mid = (lo+hi+1)/2;
        LEN = mid*2+1;
        foundLEN=0;
        if(decomp(0)) {
            lo = mid;
        } else hi = mid-1;
    }
    ans = max(ans,lo*2+1);
    cout << ans << '\n';

}

Compilation message (stderr)

lampice.cpp: In function 'void dfsD(int, F)':
lampice.cpp:131:10: warning: structured bindings only available with '-std=c++17' or '-std=gnu++17'
  131 |     auto [g,big,val] = good();
      |          ^

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