Submission #1115115

#	Time	Username	Problem	Language	Result	Execution time	Memory
1115115		VinhLuu	Palindromes (APIO14_palindrome)	C++17	0 / 100	1063 ms	4596 KiB

palindrome

#include <bits/stdc++.h>
#define ll long long
using namespace std;

const int N = 2e5 + 5;

int n, a[N];

namespace sub1{
  ll ans;
  void solve(){
    for(int i = 1; i <= n; i ++){
      stack<int> st;
      for(int j = i; j <= n; j ++){
          bool gg = true;
          int mid = (i + j) / 2;
          if((j - i + 1) & 1){
            int pl = mid - 1, pr = mid + 1;
            while(pl >= i && pr <= j){
              if(a[pl] != a[pr]){
                gg = false;
                break;
              }
              pl--;
              pr++;
            }
          }else{
            int pl = mid, pr = mid + 1;
            while(pl >= i && pr <= j){
              if(a[pl] != a[pr]){
                gg = false;
                break;
              }
              pl--;
              pr++;
            }
          }
          if(gg){
          int cnt = 0;
          for(int k = 1; k <= n - (j - i + 1) + 1; k ++){
            bool ff = true;
            for(int h = k; h <= k + (j - i + 1) - 1; h ++){
              if(a[h] != a[i + h - k]){
                ff = false;
                break;
              }
            }
            if(ff) cnt++;
          }
          ans = max(ans, 1ll * cnt * (j - i + 1));
        }
      }
    }
    cout << ans;
  }
}

namespace sub2{
  #define ull unsigned long long

  ull lt[N], f[N], g[N], base = 137;

  ull get(int l,int r){
    return f[r] - f[l] * lt[r - l + 1];
  }

  ull rev(int l,int r){
    return g[l] - g[r + 1] * lt[r - l + 1];
  }

  unordered_map<ull,int> mp;
  ll ans;

  void solve(){
    lt[0] = 1;
    for(int i = 1; i <= n; i ++){
      lt[i] = lt[i - 1] * base;
      f[i] = f[i - 1] * base + a[i];
    }
    for(int i = n; i >= 1; i --) g[i] = g[i + 1] * base + a[i];

    for(int i = 1; i <= n; i ++){
      int pl = i, pr = i;
      while(pl >= 1 && pr <= n){
        if(a[pl] != a[pr]) break;
        int val = ++mp[get(pl, pr)];
        ans = max(ans, 1ll * val * (pr - pl + 1));
      }
      pl = i, pr = i + 1;
      while(pl >= 1 && pr <= n){
        if(a[pl] != a[pr]) break;
        int val = ++mp[get(pl, pr)];
        ans = max(ans, 1ll * val * (pr - pl + 1));
      }
    }
    cout << ans;
  }
}

signed main(){
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
  #define task "palindrome"
  if(fopen(task ".inp","r")){
    freopen(task ".inp","r",stdin);
    freopen(task ".out","w",stdout);
  }

  string s; cin >> s;
  n = s.size();
  s = " " + s;
  for(int i = 1; i <= n; i ++) a[i] = (int)(s[i] - 'a' + 1);

  sub2 :: solve();

}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:104:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  104 |     freopen(task ".inp","r",stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:105:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  105 |     freopen(task ".out","w",stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~

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