Submission #817518

#	Time	Username	Problem	Language	Result	Execution time	Memory
817518		Boomyday	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	2320 ms	23376 KiB

palindromic

//
// Created by adavy on 8/9/2023.
//




#include <bits/stdc++.h>

using namespace std;

using ll = long long;
using ld = long double;
using db = double;
using str = string; // yay python!

using ii = pair<int,int>;
using pl = pair<ll,ll>;
using pd = pair<db,db>;

using vi = vector<int>;
using vb = vector<bool>;
using vl = vector<ll>;
using vd = vector<db>;
using vs = vector<str>;
using vii = vector<ii>;
using vpl = vector<pl>;
using vpd = vector<pd>;

#define tcT template<class T
#define tcTU tcT, class U

tcT> using V = vector<T>;
tcT, size_t SZ> using AR = array<T,SZ>;
tcT> using PR = pair<T,T>;

// pairs
#define mp make_pair
#define f first
#define s second

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

#define len(x) int((x).size())
#define bg(x) begin(x)
#define all(x) bg(x), end(x)
#define rall(x) rbegin(x), rend(x)
#define sor(x) sort(all(x))
#define rsz resize
#define ins insert
#define ft front()
#define bk back()
#define pb push_back
#define eb emplace_back
#define pf push_front

const int MOD = 1e9+7; // 998244353;
const int A = 998244353;
const int MX = 2e5+5;
const ll INF = 1e18; // not too close to LLONG_MAX
const ld PI = acos((ld)-1);
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1}; // for every grid problem!!

struct Modular {
    int value;
    static const int MOD_value = MOD;

    Modular(long long v = 0) { value = v % MOD; if (value < 0) value += MOD;}
    Modular(long long a, long long b) : value(0){ *this += a; *this /= b;}

    Modular& operator+=(Modular const& b) {value += b.value; if (value >= MOD) value -= MOD; return *this;}
    Modular& operator-=(Modular const& b) {value -= b.value; if (value < 0) value += MOD;return *this;}
    Modular& operator*=(Modular const& b) {value = (long long)value * b.value % MOD;return *this;}

    friend Modular mexp(Modular a, long long e);
    friend Modular inverse(Modular a) { return mexp(a, MOD - 2); }

    Modular& operator/=(Modular const& b) { return *this *= inverse(b); }
    friend Modular operator+(Modular a, Modular const b) { return a += b; }
    friend Modular operator-(Modular a, Modular const b) { return a -= b; }
    friend Modular operator-(Modular const a) { return 0 - a; }
    friend Modular operator*(Modular a, Modular const b) { return a *= b; }
    friend Modular operator/(Modular a, Modular const b) { return a /= b; }
    friend std::ostream& operator<<(std::ostream& os, Modular const& a) {return os << a.value;}
    friend bool operator==(Modular const& a, Modular const& b) {return a.value == b.value;}
    friend bool operator!=(Modular const& a, Modular const& b) {return a.value != b.value;}
};
Modular mexp(Modular a, long long e) {
    
    Modular res = 1; while (e) { if (e&1) res *= a; a *= a; e >>= 1; }
    return res;
}

void do_test(){

    string s; cin >> s;
    vector<Modular> hash;
    trav(i, s) hash.pb(i);
    F0R(i, s.size()){
        hash[i] *= mexp(A,i);
    }
    vector<Modular> prefs = {0};
    trav(i, hash) prefs.pb(prefs.back()+i);

    int ll=0,lr=0,rl=s.size()-1,rr=s.size()-1;
    int ans =0;
    while(1){

        if (lr>=rl) {
            ans += 1;

            if (lr>rl && ll==lr) ans -= 1;
            break;

        }
        Modular lhash = prefs[lr+1]-prefs[ll];
        Modular rhash = prefs[rr+1]-prefs[rl];
        rhash /= mexp(A, rl-ll);
        if (lhash == rhash){
            ans += 2;
            ll = lr+1;
            rr = rl-1;
        }
        lr++;
        rl--;
    }
    cout << ans << endl;

}

int main(){
    std::ios::sync_with_stdio(false); cin.tie(0);
    int t; cin >> t;
    F0R(i, t) do_test();
}

Compilation message (stderr)

palindromic.cpp: In function 'void do_test()':
palindromic.cpp:42:40: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   42 | #define FOR(i,a,b) for (int i = (a); i < (b); ++i)
      |                                        ^
palindromic.cpp:43:18: note: in expansion of macro 'FOR'
   43 | #define F0R(i,a) FOR(i,0,a)
      |                  ^~~
palindromic.cpp:103:5: note: in expansion of macro 'F0R'
  103 |     F0R(i, s.size()){
      |     ^~~

• Subtask 1: 15 / 15
• Subtask 2: 20 / 20
• Subtask 3: 25 / 25
• Subtask 4: 40 / 40