Submission #369183

#	Time	Username	Problem	Language	Result	Execution time	Memory
369183		ljuba	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	243 ms	20352 KiB

palindromic

#include <bits/stdc++.h>
 
using namespace std;
 
typedef long long ll;
typedef long double ld;
 
typedef vector<int> vi;
typedef vector<ll> vll;
 
typedef vector<vi> vvi;
typedef vector<vll> vvll;
 
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
 
typedef vector<pii> vpii;
typedef vector<pll> vpll;
 
typedef vector<vpii> vvpii;
typedef vector<vpll> vvpll;
 
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define sz(x) (int)(x).size()
#define fi first
#define se second
 
template<class T> bool ckmin(T &a, const T &b) {return a > b ? a = b, 1 : 0;}
template<class T> bool ckmax(T &a, const T &b) {return a < b ? a = b, 1 : 0;}
 
void __print(int x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
 
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for(auto z : x) cerr << (f++ ? "," : ""), __print(z); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if(sizeof...(v)) cerr << ", "; _print(v...);}
 
#ifdef ljuba
#define dbg(x...) cerr << "LINE(" << __LINE__ << ") -> " << "[" << #x << "] = ["; _print(x)
#else
#define dbg(x...)
#endif
 
const char nl = '\n';

const int MOD = 1e9 + 7;
const int p = 31;

inline int mul(int a, int b) {
    return (a * 1LL * b) % MOD;
}

inline int add(int a, int b) {
    return (a + b) % MOD;
}

inline int sub(int a, int b) {
    return (a - b + MOD) % MOD;
}

void solve() {
    string s;
    cin >> s;
    int n = sz(s);

    int tren = p;
    vi hsh(n+1);
    for(int i = 0; i < n; ++i) {
        hsh[i+1] = add(hsh[i], mul(tren, (s[i]-'a'+1)));
        tren = mul(tren, p);
    }
    vi inv(n+1);
    inv[0] = 1;
    for(int i = 1; i <= n; ++i) {
        inv[i] = mul(inv[i-1], 129032259);
    }

    int ans = 0;
    int posl = 1;
    int posl2 = n;

    for(int i = 1; i <= n / 2; ++i) {
        int hes1 = mul(sub(hsh[i], hsh[posl-1]), inv[posl-1]);
        int hes2 = mul(sub(hsh[posl2], hsh[n-i]), inv[n-i]);
        if(hes1 == hes2) {
            ans += 2;
            posl = i + 1;
            posl2 = n - i;
        }
    }

    dbg(posl, posl2);

    ans += (posl <= posl2);

    cout << ans << nl;
}
 
int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    int testCases = 1;
    cin >> testCases;
    while(testCases--)
        solve();
 
}

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