Submission #716224

#	Time	Username	Problem	Language	Result	Execution time	Memory
716224		arush_agu	Palindromes (APIO14_palindrome)	C++17	0 / 100	1067 ms	9300 KiB

palindrome

#include <algorithm>
#include <cctype>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <functional>
#include <iomanip>
#include <iostream>
#include <iterator>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

#ifdef DEBUG
#include <time.h>
#endif

#define all(a) (a).begin(), (a).end()
#define rev(a) (a).rbegin(), (a).rend()
#define F first
#define S second
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x)                                                                 \
  {                                                                            \
    ++recur_depth;                                                             \
    auto x_ = x;                                                               \
    --recur_depth;                                                             \
    cerr << string(recur_depth, '\t') << "\e[91m" << __func__ << ":"           \
         << __LINE__ << "\t" << #x << " = " << x_ << "\e[39m" << endl;         \
  }
#else
#define dbg(x)
#endif

using namespace std;
using namespace __gnu_pbds;

typedef pair<int, int> ii;

typedef long long ll;
typedef long double ld;
typedef pair<ll, ll> llll;

typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<pair<int, int>> vii;
typedef vector<vii> vvii;

typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<pair<ll, ll>> vll;
typedef vector<vll> vvll;

typedef vector<bool> vb;

template <class type1>
using ordered_set = tree<type1, null_type, less<type1>, rb_tree_tag,
                         tree_order_statistics_node_update>;

template <typename A, typename B>
ostream &operator<<(ostream &os, const pair<A, B> &p) {
  return os << '(' << p.first << ", " << p.second << ')';
}
template <typename T_container, typename T = typename enable_if<
                                    !is_same<T_container, string>::value,
                                    typename T_container::value_type>::type>
ostream &operator<<(ostream &os, const T_container &v) {
  os << '{';
  string sep;
  for (const T &x : v)
    os << sep << x, sep = ", ";
  return os << '}';
}

const ll MOD = 1e9 + 7;
// const ll MOD = 998244353;
const ll INF = 1e9;
const ld EPS = 1e-9;

void solve() {
  string s; cin >> s;
  int n = s.size();

  // vvl hash(n, vl(n));
  // for (int i=0; i<n; i++) {
  //   ll p = 31, m = MOD, h = 0, p_pow = 1;
  //   for (int j=i; j<n; j++) {
  //     hash[i][j] = h = (h + (s[j] - 'a' + 1) * p_pow) % m;
  //     p_pow = (p_pow * p) % m;
  //   }
  // }
  
  vl hash(n), ppow(n + 1);
  ll p = 31, m = MOD, h = 0, p_pow = 1;
  for (int j=0; j<n; j++) {
    hash[j] = h = (h + (s[j] - 'a' + 1) * p_pow) % m;
    ppow[j] = p_pow;
    p_pow = (p_pow * p) % m;
  }
  ppow[n] = p_pow;


  auto bin_pow = [&](ll a, ll b) {
    ll res = 1;
    while (b) {
      if (b & 1) res *= a, res %= MOD;
      a *= a, a %= MOD;
      b >>= 1;
    }
    return res;
  };

  vl ppow_inv(n + 1);
  for (int i=0; i<=n; i++) {
    ppow_inv[i] = bin_pow(ppow[i], MOD - 2);
  }

  auto get_hash = [&](int i, int j) {
    ll h_pi = i == 0 ? 0 : hash[i - 1];
    return ((hash[j] - h_pi) * ppow_inv[i] + MOD) % MOD;
  };

  unordered_map<ll, llll> cnt;
  for (int i=0; i<n; i++) {
    for (int sz=0; i-sz >= 0 && i + sz < n; sz++) {
      if (s[i - sz] != s[i + sz]) break;
      ll h = get_hash(i - sz, i + sz);
      if (cnt.count(h)) cnt[h].second++;
      else
        cnt[h] = {2 * sz + 1, 1};
    }

    if (i > 0 && s[i] == s[i - 1]) {
      for (int sz=0; i - sz - 1 >= 0 && i + sz < n; sz++) {
        if (s[i - sz - 1] != s[i + sz]) break;
        ll h = get_hash(i - sz - 1, i + sz);
        if (cnt.count(h)) cnt[h].second++;
        else
          cnt[h] = {2 * sz + 2, 1};
        // cnt[{hash[i - sz - 1][i + sz], 2 * sz + 2}]++;
      }
    }
  }

  ll ans = -INF;
  for (auto [x, c] : cnt) {
    ans = max(ans, c.second * c.first);
  }
  cout << ans << "\n";
}

int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(NULL);

  clock_t start = clock();

  int test_cases = 1;
  /* cin >> test_cases; */

  while (test_cases--)
    solve();

#ifdef DEBUG
  cerr << fixed << setprecision(10)
       << "\nTime Taken: " << (double)(clock() - start) / CLOCKS_PER_SEC
       << "s\n";
#endif
  return 0;
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:167:11: warning: unused variable 'start' [-Wunused-variable]
  167 |   clock_t start = clock();
      |           ^~~~~

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