Submission #1126414

#	Time	Username	Problem	Language	Result	Execution time	Memory
1126414		luvna	Palindromic Partitions (CEOI17_palindromic)	C++20	100 / 100	120 ms	11204 KiB

palindromic

#include<bits/stdc++.h>

#define MASK(i) (1 << (i))
#define pub push_back
#define all(v) v.begin(), v.end()
#define compact(v) v.erase(unique(all(v)), end(v))
#define pii pair<int,int>
#define fi first
#define se second
#define endl "\n"
#define sz(v) (int)(v).size()
#define dbg(x) "[" #x " = " << (x) << "]"

using namespace std;

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

typedef long long ll;
typedef long double ld;

mt19937 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r){return uniform_int_distribution<ll>(l, r)(rng);}

const int N = 1e6 + 15;
const int base = 311;
const int MOD = 998244353;

int add(int a, int b) {if(a >= MOD - b) return a - MOD + b; return a + b;}
int sub(int a, int b) {if(a < b) return a + MOD - b; return a - b;}
int mul(int a, int b) {return 1LL*a*b % MOD;}

int pw[N];

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

    int n = sz(s);

    s = '.' + s;

    vector<int> H(n + 15, 0);

    for(int i = 1; i <= n; i++) H[i] = add(mul(H[i-1], base), s[i]);

    auto get_pref = [&](int l, int r) -> int{
        return sub(H[r], mul(H[l-1], pw[r - l + 1]));
    };

    int l = 1, r = n, st = 1, en = n;

    int res = 0;

    while(l < r){
        if(get_pref(st,l) == get_pref(r,en)){
            //cout << st << " " << l << "   " << r << " " << en << endl;
            res += 2;
            st = l+1;
            en = r-1;
            if(l + 1 == r) break;
        }
        if(en < st) break;
        l++;
        r--;
    }

    res += (l >= r);

    cout << res << endl;
}

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

    #define task "task"

    if(fopen(task".INP", "r")){
        freopen(task".INP", "r", stdin);
        freopen(task".OUT", "w", stdout);
    }

    pw[0] = 1;
    for(int i = 1; i < N; i++) pw[i] = mul(pw[i-1], base);

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

Compilation message (stderr)

palindromic.cpp: In function 'int main()':
palindromic.cpp:79:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   79 |         freopen(task".INP", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
palindromic.cpp:80:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   80 |         freopen(task".OUT", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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