Submission #395758

#	Time	Username	Problem	Language	Result	Execution time	Memory
395758		SavicS	Palindromes (APIO14_palindrome)	C++14	47 / 100	1091 ms	37076 KiB

palindrome

#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <bits/stdc++.h>

#define fi first
#define se second
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) a.begin(), a.end()
#define rall(a) a.rbegin(), a.rend()
#define ff(i,a,b) for(int i=a;i<=b;i++)
#define fb(i,b,a) for(int i=b;i>=a;i--)

using namespace std;
using namespace __gnu_pbds;
typedef long long ll;
typedef pair<int,int> pii;
const int maxn = 300005;
const int inf = 1e9 + 5;

template<typename T>
using ordered_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

// os.order_of_key(k) the number of elements in the os less than k
// *os.find_by_order(k)  print the k-th smallest number in os(0-based)

int n;
string s;

struct palindromic_tree {
    int N;
    int idx;
    int last;
    int a[maxn];
    int len[maxn];
    int cnt[maxn];
    int fail[maxn];
    int lenj[maxn];
    int son[maxn][26];

    int new_node(int X) {
        memset(son[idx], 0, sizeof(son[idx]));
        len[idx] = X;
        cnt[idx] = 0;
        return idx++;
    }

    void init() {
        N = 0, last = 0, idx = 0;
        new_node(0), new_node(-1);
        fail[0] = 1;
        a[0] = -1;
    }

    int get_fail(int X) {
        while(a[N - len[X] - 1] != a[N])X = fail[X];
        return X;
    }

    void add(int X) {
        X -= 'a';
        a[++N] = X;

        int cur = get_fail(last);
        if(!son[cur][X]) {
            int nw = new_node(len[cur] + 2);
            fail[nw] = son[get_fail(fail[cur])][X];
            son[cur][X] = nw;
        }

        last = son[cur][X];
        lenj[last] += 1;
    }

    void update() {
        fb(i,idx - 1, 0) {

            int X = i;
            while(X != 0) {
                cnt[X] += lenj[i];
                X = fail[X];
            }

            lenj[i] = 0;
        }
    }

} P;

int main() 
{
    ios::sync_with_stdio(false);
    cout.tie(nullptr);
    cin.tie(nullptr);
    cin >> s;
    n = sz(s);

    P.init();
    ff(i,0,n - 1)P.add(s[i]);
    P.update();

    ll rez = 0;
    ff(i,0,P.idx - 1)rez = max(rez, 1ll * P.len[i] * P.cnt[i]);
    cout << rez << endl;

    return 0;
}
/**

abacaba

www

// probati bojenje sahovski ili slicno

**/

• Subtask 1: 8 / 8
• Subtask 2: 15 / 15
• Subtask 3: 24 / 24
• Subtask 4: 0 / 26
• Subtask 5: 0 / 27