Submission #564931

#TimeUsernameProblemLanguageResultExecution timeMemory
564931ac2huPalindromes (APIO14_palindrome)C++14
0 / 100
302 ms131072 KiB
#include <bits/stdc++.h> #ifdef DEBUG #include "../templates/debug.h" #else #define deb(x...) #endif using namespace std; typedef unsigned long long ull; // Generate random base in (before, after) open interval: int gen_base(const int before, const int after) { auto seed = std::chrono::high_resolution_clock::now().time_since_epoch().count(); std::mt19937 mt_rand(seed); int base = std::uniform_int_distribution<int>(before+1, after)(mt_rand); return base % 2 == 0 ? base-1 : base; } struct PolyHash {/*{{{*/ // -------- Static variables -------- static const int mod = (int)1e9+123; // prime mod of polynomial hashing static std::vector<int> pow1; // powers of base modulo mod static std::vector<ull> pow2; // powers of base modulo 2^64 static int base; // base (point of hashing) // --------- Static functons -------- static inline int diff(int a, int b) { // Diff between `a` and `b` modulo mod (0 <= a < mod, 0 <= b < mod) return (a -= b) < 0 ? a + mod : a; } // -------------- Variables of class ------------- std::vector<int> pref1; // Hash on prefix modulo mod std::vector<ull> pref2; // Hash on prefix modulo 2^64 // Cunstructor from string: PolyHash(const std::string& s) : pref1(s.size()+1u, 0) , pref2(s.size()+1u, 0) { assert(base < mod); const int n = s.size(); // Firstly calculated needed power of base: while ((int)pow1.size() <= n) { pow1.push_back(1LL * pow1.back() * base % mod); pow2.push_back(pow2.back() * base); } for (int i = 0; i < n; ++i) { // Fill arrays with polynomial hashes on prefix assert(base > s[i]); pref1[i+1] = (pref1[i] + 1LL * s[i] * pow1[i]) % mod; pref2[i+1] = pref2[i] + s[i] * pow2[i]; } } // Polynomial hash of subsequence [pos, pos+len) // If mxPow != 0, value automatically multiply on base in needed power. Finally base ^ mxPow inline std::pair<int, ull> operator()(const int pos, const int len, const int mxPow = 0) const { int hash1 = pref1[pos+len] - pref1[pos]; ull hash2 = pref2[pos+len] - pref2[pos]; if (hash1 < 0) hash1 += mod; if (mxPow != 0) { hash1 = 1LL * hash1 * pow1[mxPow-(pos+len-1)] % mod; hash2 *= pow2[mxPow-(pos+len-1)]; } return std::make_pair(hash1, hash2); } };/*}}}*/ int PolyHash::base((int)1e9 + 7); vector<int> PolyHash::pow1{1}; vector<ull> PolyHash::pow2{1}; int brute(string s){ // O(n^2) is easy // Find all palindromes and put it in a map and then itterate to find maximum int n = s.size(); vector<vector<bool>> is_pali(n, vector<bool>(n)); for(int siz = 0;siz<n;siz++){ for(int i = 0;i + siz<n;i++){ int j = i + siz; if(siz == 0)is_pali[i][j] = true; else if(siz == 1)is_pali[i][j] = (s[i] == s[j]); else is_pali[i][j] = ((s[i] == s[j])&&is_pali[i + 1][j - 1]); } } PolyHash hs(s); // map<pair<int,ull>, int> ma; vector<int> mx(n + 1, 0); for(int siz = 0;siz<n;siz++){ for(int i = 0;i+siz<n;i++){ int j = i + siz; if(is_pali[i][j]){ auto temp = hs(i, siz + 1, n); // ma[temp]++; // mx[siz + 1] = max(mx[siz + 1], ma[temp]); } } } // deb(ma); int ans = 0; // for(int i = 0;i<n + 1;i++){ // ans = max(ans, i*mx[i]); // } return ans; } signed main(){ string s;cin >> s; cout << brute(s) << "\n"; }

Compilation message (stderr)

palindrome.cpp: In function 'int brute(std::string)':
palindrome.cpp:90:22: warning: variable 'temp' set but not used [-Wunused-but-set-variable]
   90 |                 auto temp = hs(i, siz + 1, n);
      |                      ^~~~
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