Submission #676328

#	Time	Username	Problem	Language	Result	Execution time	Memory
676328		vuavisao	Palindromes (APIO14_palindrome)	C++14	23 / 100	1082 ms	988 KiB

palindrome

#include<bits/stdc++.h>
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#define ll long long
using namespace std;

template<typename Lhs, typename Rhs> inline bool Max_self(Lhs &a, Rhs b) { if(b > a) { a = b; return true; } return false; }
template<typename Lhs, typename Rhs> inline bool Min_self(Lhs &a, Rhs b) { if(b < a) { a = b; return true; } return false; }

const int N = 3e5 + 10;

int n;
string s;

namespace sub123 {
    bool check() {
        return n <= 10000;
    }

    const int BASE = 128;
    const int MOD = 1e9 + 7;

    int p[N], h[N], h_rev[N];
    int res;

    int get_hash(int l, int r, int* h) {
        return (h[r] - 1ll * h[l - 1] * p[r - l + 1] % MOD + MOD) % MOD;
    }


    void solve() {
        p[0] = 1;
        for(int i = 1; i <= n; ++ i) {
            p[i] = 1ll * p[i - 1] * BASE % MOD;
            h[i] = (1ll * h[i - 1] * BASE + s[i]) % MOD;
            h_rev[i] = (1ll * h_rev[i - 1] * BASE + s[n - i + 1]) % MOD;
        }
        for(int len = 1; len <= n; ++ len) {
            unordered_map<int, int> mpp;
            auto palin = [&] (int l, int r) -> bool {
                return get_hash(l, r, h) == get_hash(n - r + 1, n - l + 1, h_rev);
            };
            for(int i = 1; i <= n - len + 1; ++ i) {
                if(palin(i, i + len - 1)) {
                    int hash = get_hash(i, i + len - 1, h);
                    ++ mpp[hash];
                    Max_self(res, mpp[hash] * len);
                }
            }
        }
        cout << res;
    }
}

int32_t main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    if (fopen("APIO14_palindrome.inp", "r")) {
        freopen("APIO14_palindrome.inp", "r", stdin);
        freopen("APIO14_palindrome.out", "w", stdout);
    }
    cin >> s; n = (int) s.size(); s = ' ' + s;
    if(sub123::check()) {
        sub123::solve();
        return 0;
    }
    return 0;
}

/// Code by vuavisao

Compilation message (stderr)

palindrome.cpp: In function 'int32_t main()':
palindrome.cpp:60:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   60 |         freopen("APIO14_palindrome.inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:61:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   61 |         freopen("APIO14_palindrome.out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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