Submission #439912

#	Time	Username	Problem	Language	Result	Execution time	Memory
439912		codebuster_10	Palindromes (APIO14_palindrome)	C++17	100 / 100	68 ms	69740 KiB

palindrome

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

#define int int64_t //be careful about this 
#define endl "\n"
#define f(i,a,b) for(int i=int(a);i<int(b);++i)

#define pr pair
#define ar array
#define fr first
#define sc second
#define vt vector
#define pb push_back
#define eb emplace_back

#define SZ(x) ((int)(x).size())
#define all(a) (a).begin(),(a).end()
#define allr(a) (a).rbegin(),(a).rend()
#define mem(a,b) memset(a, b, sizeof(a))

template<class A> void rd(vt<A>& v);
template<class T> void rd(T& x){ cin >> x;}
template<class H, class... T> void rd(H& h, T&... t) { rd(h); rd(t...);}
template<class A> void rd(vt<A>& x) { for(auto& a : x) rd(a);}

template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0;}
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0;}

template<typename T>
void __p(T a) {
  cout<<a; 
}
template<typename T, typename F>
void __p(pair<T, F> a) {
  cout<<"{";
  __p(a.first);
  cout<<",";
  __p(a.second);
  cout<<"}\n"; 
}
template<typename T>
void __p(std::vector<T> a) {
  cout<<"{";
  for(auto it=a.begin(); it<a.end(); it++)
    __p(*it),cout<<",}\n"[it+1==a.end()]; 
}
template<typename T, typename ...Arg>
void __p(T a1, Arg ...a) {
  __p(a1);
  __p(a...);
}
template<typename Arg1>
void __f(const char *name, Arg1 &&arg1) {
  cout<<name<<" : ";
  __p(arg1);
  cout<<endl;
}
template<typename Arg1, typename ... Args>
void __f(const char *names, Arg1 &&arg1, Args &&... args) {
  int bracket=0,i=0;
  for(;; i++)
    if(names[i]==','&&bracket==0)
      break;
    else if(names[i]=='(')
      bracket++;
    else if(names[i]==')')
      bracket--;
  const char *comma=names+i;
  cout.write(names,comma-names)<<" : ";
  __p(arg1);
  cout<<" | ";
  __f(comma+1,args...);
}


void setIO(string s = "") {
  ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0); 
  // remove this when size of input is not fixed.
  cin.exceptions(cin.failbit); 
	cout.precision(15);	cout << fixed;
  if(SZ(s)){
  	freopen((s+".in").c_str(),"r",stdin);
  	freopen((s+".out").c_str(),"w",stdout);
  }
}


/*********************************************Look Below******************************************************************/








































/*
	* description :- palindromic tree for a string which is genralized version of kmp for palindromes.
	* indexing of palindromic tree starts from 1.
	* source :- http://adilet.org/blog/palindromic-tree/.
	* verification :- https://www.spoj.com/status/NUMOFPAL,deepkamal/
*/

template<int MAX_N,int ALPHABET>
struct palindromic_tree {
	
	static const int INF = 1e9;
	
	struct node {
		// the next node which stores c + palindrome + c
  	array<int,ALPHABET> next;
  	// length of the current palindrome
  	int length;
  	// maximum proper suffix of the current palindrome which is also a palindrome.
  	int suffix_link; 
  	// lazy value.
  	int lazy;
  	node(){
  		next.fill(-INF);
  		length = suffix_link = lazy = -INF;
  	}
	};

	// our string
	string s; 
	// our palindromic tree
	node tree[MAX_N];
	// total number of nodes
	int total_nodes;           
	// maximum suffix palindrome of present string.
	int max_suffix;	
	
	palindromic_tree() {
		// node 1 - root with length -1, node 2 - root with length 0
    tree[1].length = -1, tree[1].suffix_link = 1,	tree[1].lazy = 0;
    tree[2].length = 0, tree[2].suffix_link = 1,	tree[2].lazy = 0;
    total_nodes = 2; 
    max_suffix = 2;
	}
	
	bool add_char(char _c) {
		s.push_back(_c);
		int pos = int(s.size()) - 1;
		
  	int cur_suffix = max_suffix, cur_length = 0;
  	int c = s[pos] - 'a';

  	while(true){
      cur_length = tree[cur_suffix].length;
      if(pos - 1 - cur_length >= 0 && s[pos - 1 - cur_length] == s[pos]){
      	break;  
      } 
      cur_suffix = tree[cur_suffix].suffix_link;
  	}       
  	
  	if(tree[cur_suffix].next[c] > 0){  
      max_suffix = tree[cur_suffix].next[c];
      ++tree[max_suffix].lazy;
      return false;
  	}

  	int now = ++total_nodes;
  	
  	max_suffix = now;
  	tree[now].length = tree[cur_suffix].length + 2;
  	tree[cur_suffix].next[c] = now;
  	tree[now].lazy = 1;
  	
  	if(tree[now].length == 1){
    	tree[now].suffix_link = 2;
    	return true;
  	}

  	while(true){
    	cur_suffix = tree[cur_suffix].suffix_link;
    	cur_length = tree[cur_suffix].length;
    	if(pos - 1 - cur_length >= 0 && s[pos - 1 - cur_length] == s[pos]){
        tree[now].suffix_link = tree[cur_suffix].next[c];
        break;
    	}       
  	}          
  	return true;
	}
	
	void fun(){
		
		int best = 0;
		
		for(int i = total_nodes; i >= 1; --i){
			int j = tree[i].suffix_link;
			tree[j].lazy += tree[i].lazy;
			ckmax(best,tree[i].length * tree[i].lazy);
		}
		
		cout << best;
		
		return;
		
	}
};


palindromic_tree<300077,26> pdt;

signed main(){
  setIO();
	string s; rd(s);
	for(auto c : s) pdt.add_char(c);
	pdt.fun();
}

Compilation message (stderr)

palindrome.cpp: In function 'void setIO(std::string)':
palindrome.cpp:82:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   82 |    freopen((s+".in").c_str(),"r",stdin);
      |    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:83:11: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   83 |    freopen((s+".out").c_str(),"w",stdout);
      |    ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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