Submission #173655

#	Time	Username	Problem	Language	Result	Execution time	Memory
173655		Nucleist	Palindromes (APIO14_palindrome)	C++14	23 / 100	1073 ms	7760 KiB

palindrome

#include<bits/stdc++.h> 
using namespace std; 
void expand(string str, int low, int high, auto &set)
{
  // run till str[low.high] is a palindrome
  while (low >= 0 && high < str.length()
      && str[low] == str[high])
  {
    // push all palindromes into the set
    set.insert(str.substr(low, high - low + 1));

    // expand in both directions
    low--, high++;
  }
}
int ans=0;
string a;
vector<int> rabin_karp(string const& s, string const& t) {
    const int p = 31; 
    const int m = 1e9 + 9;
    int S = s.size(), T = t.size();

    vector<long long> p_pow(max(S, T)); 
    p_pow[0] = 1; 
    for (int i = 1; i < (int)p_pow.size(); i++) 
        p_pow[i] = (p_pow[i-1] * p) % m;

    vector<long long> h(T + 1, 0); 
    for (int i = 0; i < T; i++)
        h[i+1] = (h[i] + (t[i] - 'a' + 1) * p_pow[i]) % m; 
    long long h_s = 0; 
    for (int i = 0; i < S; i++) 
        h_s = (h_s + (s[i] - 'a' + 1) * p_pow[i]) % m; 

    vector<int> occurences;
    for (int i = 0; i + S - 1 < T; i++) { 
        long long cur_h = (h[i+S] + m - h[i]) % m; 
        if (cur_h == h_s * p_pow[i] % m)
            occurences.push_back(i);
    }
    return occurences;
}
void allPalindromicSubstrings(string str)
{
  unordered_set<string> set;

  for (int i = 0; i < str.length(); i++)
  {
    expand(str, i, i, set);
    expand(str, i, i + 1, set);
  }
  for (auto i : set)
   ans=max(ans,(int)((rabin_karp(i,a).size())*i.size()));
}

int main() 
{ 
    cin>>a;
    allPalindromicSubstrings(a); 
    cout<<ans;
} 

Compilation message (stderr)

palindrome.cpp: In function 'void allPalindromicSubstrings(std::__cxx11::string)':
palindrome.cpp:47:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int i = 0; i < str.length(); i++)
                   ~~^~~~~~~~~~~~~~
palindrome.cpp: In instantiation of 'void expand(std::__cxx11::string, int, int, auto:1&) [with auto:1 = std::unordered_set<std::__cxx11::basic_string<char> >; std::__cxx11::string = std::__cxx11::basic_string<char>]':
palindrome.cpp:49:26:   required from here
palindrome.cpp:6:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   while (low >= 0 && high < str.length()
                      ~~~~~^~~~~~~~~~~~~~

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