Submission #716455

#	Time	Username	Problem	Language	Result	Execution time	Memory
716455		arush_agu	Palindromes (APIO14_palindrome)	C++17	100 / 100	120 ms	104496 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;

const int MAXN = 3e5 + 10;

// Saw Solution

struct PalindromeTree {
  struct Node {
    ll label[26], suff, len, cnt_suff;
    vi eds;

    Node() {
      for (int i=0; i<26; i++) label[i] = -1;
    }
  } tree[MAXN + 100];
  string s;
  int curr_node, cnt_node;

  void init(string s_) {
    tree[0].len = -1;
    tree[0].suff = 0;

    tree[1].len = 0;
    tree[1].suff = 0;

    tree[0].eds.push_back(1);
    curr_node = cnt_node = 1;
    s = s_;

    for (int i=0; i<s.size(); i++) add(i);
  }

  void add(int idx) {
    int curr = curr_node;
    int c = s[idx] - 'a';

    while (1) {
      if (idx - tree[curr].len - 1 >= 0 && s[idx - tree[curr].len - 1] == s[idx]) break;
      curr = tree[curr].suff;
    }

    if (tree[curr].label[c] != -1) {
      curr_node = tree[curr].label[c];
      tree[curr_node].cnt_suff++;
      return;
    }

    curr_node = ++cnt_node;
    tree[curr].label[c] = curr_node;
    tree[curr_node].len = tree[curr].len + 2;
    tree[curr_node].cnt_suff = 1;

    if (curr == 0) {
      tree[curr_node].suff = 1;
      tree[1].eds.push_back(curr_node);
      return;
    }

    while (1) {
      curr = tree[curr].suff;
      if (idx - tree[curr].len - 1 >= 0 && s[idx - tree[curr].len - 1] == s[idx]) {
        tree[curr_node].suff = tree[curr].label[c];
        tree[tree[curr].label[c]].eds.push_back(curr_node);
        break;
      }
    }
  }

  ll get_score() {
    ll ans = -INF;
    function<void(int)> f = [&](int u) {
      for (int &v : tree[u].eds) {
        f(v);
        tree[u].cnt_suff += tree[v].cnt_suff;
      }
      ans = max(ans, tree[u].cnt_suff * tree[u].len);
    }; f(0);
    return ans;
  }
} pt;

void solve() {
  string s; cin >> s;
  pt.init(s);

  cout << pt.get_score() << "\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 member function 'void PalindromeTree::init(std::string)':
palindrome.cpp:118:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::__cxx11::basic_string<char>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  118 |     for (int i=0; i<s.size(); i++) add(i);
      |                   ~^~~~~~~~~
palindrome.cpp: In function 'int main()':
palindrome.cpp:181:11: warning: unused variable 'start' [-Wunused-variable]
  181 |   clock_t start = clock();
      |           ^~~~~

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