Submission #915858

#	Time	Username	Problem	Language	Result	Execution time	Memory
915858		vjudge1	Palindromic Partitions (CEOI17_palindromic)	C++17	100 / 100	203 ms	18876 KiB

palindromic

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;

// author : a1abay
// (a / b) % c = (a * b ^ (mod - 2)) % c;
 
#define pb          push_back
#define pii         pair<int, int>
#define pll         pair<ll, ll>
#define all(v)      v.begin(), v.end()
#define whole(a)    a+1, a+1+n
#define se          second
#define fi          first
#define int         ll
#define print(k)    cerr << "Ans : "; cout << k << endl;
#define ins         insert
#define bpc         __builtin_popcountll
#define skip        continue
#define endll          '\n'
#define gcd(a, b)   __gcd(a, b)
#define lcm(a, b)   (a*b / (__gcd(a, b)))
#define mpr         make_pair
#define ordered_set tree<int, null_type,less<int>, rb_tree_tag,tree_order_statistics_node_update> 

typedef long long           ll;
typedef unsigned long long  ull;
typedef long double         ld;
const int sz =              1e6 + 5;
using namespace             std;

void open(string s, string f)
{
    freopen((s + ".txt").c_str(), "r", stdin);
    freopen((f + ".txt").c_str(), "w", stdout);
}

int mod = 1e9 + 7;
int P = 53;

int n, p[sz], pr[sz], sf[sz];

bool check(int l, int lx, int r, int rx)
{
    int a = (pr[l] - pr[lx] + mod) % mod;
    int b = (pr[rx - 1] - pr[r - 1] + mod) % mod;
    return a * p[r - lx - 1] % mod == b;
}

void solve()
{
    string s;
    cin >> s;

    n = s.size();
    
    p[0] = 1;
    for(int i = 1; i <= n; i++)
    {
        p[i] = p[i - 1] * P % mod;
        pr[i] = pr[i - 1] + (s[i - 1] - 'a' + 1) * p[i] % mod;
    }

    int l = 1, r = n, lx = 0, rx = n + 1, ans = 0;
    while(l < r)
    {
        if(check(l, lx, r, rx))
        {
            ans += 2;
            lx = l;
            rx = r;
        }
        l++;
        r--;
    }
    if(lx + 1 != rx)ans++;

    cout << ans << '\n';

}   

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

    // open("in", "out");

    int t = 1;
    cin >> t;

    while(t--)
    {
        solve();
    }
}  

Compilation message (stderr)

palindromic.cpp: In function 'void open(std::string, std::string)':
palindromic.cpp:35:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |     freopen((s + ".txt").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
palindromic.cpp:36:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   36 |     freopen((f + ".txt").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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