Submission #901624

#	Time	Username	Problem	Language	Result	Execution time	Memory
901624		alexandru_onut	Palindromes (APIO14_palindrome)	C++14	0 / 100	2 ms	348 KiB

palindrome

#include <bits/stdc++.h>

using namespace std;

string A;

int zF (const string &str)
{
    string aux = str + "#" + A;
    int N = aux.size();
    vector <int> z (N , 0);
    int L = 0 , R = 0 , ans = 0;
    for(int i = 0; i < N; ++i)
    {
        if(i < R)
            z[i] = min(z[i - L] , R - i);
        while(i + z[i] < N && aux[z[i]] == aux[i + z[i]])
            ++z[i];
        if(i + z[i] > R)
        {
            R = i + z[i];
            L = i;
        }
        ans += (z[i] == str.size());
    }
    return ans;
}

long long Manacher (const string &str)
{
    string S;
    vector <int> dp;
    S.push_back('#');
    for(int i = 0; i < (int) str.size(); ++i)
    {
        S.push_back(str[i]);
        S.push_back('#');
    }
    int N = S.size();
    dp = vector <int> (N , 0);
    int C = 0 , R = 0;
    for(int i = 0; i < N; ++i)
    {
        int M = 2 * C - i;
        if(i < R)
            dp[i] = min(dp[M] , R - i);
        int a = i + (dp[i] + 1);
        int b = i - (dp[i] + 1);
        while(b >= 0 && a < N && S[a] == S[b])
            ++dp[i] , ++a , --b;
        if(i + dp[i] > R)
        {
            C = i;
            R = i + dp[i];
        }
    }
    int p = 0;
    string ans;
    unordered_map <string , bool> use;
    long long rasp = 0;
    for(int i = 1; i < (int) S.size(); ++i)
    {
        string ans;
        for(int j = i - dp[i]; j <= i + dp[i]; ++j)
            if(S[j] != '#')
                ans.push_back(S[j]);
        long long nrAp = zF (ans) * ans.size();
        if(!use[ans])
            rasp = max(rasp , 1LL * nrAp) , use[ans] = 1;
    }
    return rasp;
}

int main()
{
    ios_base :: sync_with_stdio(false); cin.tie(nullptr);
    freopen ("palindrome.in" , "r" , stdin);
    freopen ("palindrome.out" , "w" , stdout);
    cin >> A;
    cout << Manacher(A);
}

Compilation message (stderr)

palindrome.cpp: In function 'int zF(const string&)':
palindrome.cpp:24:22: warning: comparison of integer expressions of different signedness: '__gnu_cxx::__alloc_traits<std::allocator<int>, int>::value_type' {aka 'int'} and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |         ans += (z[i] == str.size());
palindrome.cpp: In function 'long long int Manacher(const string&)':
palindrome.cpp:57:9: warning: unused variable 'p' [-Wunused-variable]
   57 |     int p = 0;
      |         ^
palindrome.cpp: In function 'int main()':
palindrome.cpp:77:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   77 |     freopen ("palindrome.in" , "r" , stdin);
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:78:13: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   78 |     freopen ("palindrome.out" , "w" , stdout);
      |     ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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