Submission #312128

#	Time	Username	Problem	Language	Result	Execution time	Memory
312128		hohohaha	Palindromes (APIO14_palindrome)	C++14	0 / 100	86 ms	18016 KiB

palindrome

#include<bits/stdc++.h>

using namespace std;

#define int long long

#define ii pair<int, int>
#define iii pair<ii, int>

#define mp make_pair
#define eb emplace_back

#define vi vector<int>
#define vii vector<ii>
#define viii vector<iii>

#define fi first
#define se second
#define xx fi.fi
#define yy fi.se
#define zz se
int n, mhash[600005], rnk[600005], sa[600005], lcp[600005], even[600006], odd[600005], h[600005], ans;
stack<int> st;
string s;
int f(int a, int b, int c)
{
	assert(a<=1e6 and b<=1e6);
	return a*(int)1e12+b*(int)1e6+c;
}
void build(int len, int N)
{
	if(len==1) 
	{
		for(int i=1; i+len-1<=N; i++)
		{
			mhash[i] = (int)s[i];
		}
	}
	else
	{
		map<int, int> M;
		int hlf = len>>1;
		build(hlf, N);
		for(int i=1; i+len-1<=N; i++)
		{
			mhash[i] = f(mhash[i], mhash[i+hlf], (len&1? (int)s[i+len-1]: 0));
			M[mhash[i]] = 0;
		}
		int curp = 0;
		for(auto& x: M)
		{
			x.se = ++curp;
		}
		for(int i=1; i+len-1<=N; i++)
		{
			mhash[i] = M[mhash[i]];
		}
	}
}
bool cmp(int a, int b)
{
	return mhash[a]<mhash[b];
}
signed main()
{
// 	freopen(".inp", "r", stdin);
// 	freopen(".out", "w", stdout);
 	ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    cin>>s; n = s.length();
    s = "$"+s+char('a'-1)+s;
    build(n, n);
    for(int i=1; i<=n; i++)
    {
    	sa[i] = i;
	}
	sort(sa+1, sa+n+1, cmp);
	for(int i=1; i<=n; i++)
	{
		rnk[sa[i]] = i;
	}
	int curl = 0;
	for(int i=1; i<=n; i++)
	{
		if(rnk[i]==n) 
		{
			lcp[rnk[i]] = 0;
			continue;
		}
		int j = sa[rnk[i]+1];
		while(s[i+curl]==s[j+curl])
		{
			curl++;
		}
		lcp[rnk[i]] = curl;
		if(curl) curl--;
	}
	int l = 0, r = 0;
	for(int i=1; i<=n; i++)
	{
		if(l<=i and i<=r)
		{
			odd[i] = odd[l+r-i];
		}
		while(i-odd[i]>=1 and i+odd[i]<=n and s[i-odd[i]]==s[i+odd[i]]) 
		{
			odd[i]++;
		}
		if(odd[i] and r<i+odd[i]-1)
		{
			r = i+odd[i]-1;
			l = i-odd[i]+1;
		}
	}
	l = 0, r = 0;
	for(int i=2; i<=n; i++)
	{
		if(l<=i-1 and i<=r)
		{
			even[i] = even[l+r-i+1];
		}
		while(i-1-even[i]>=1 and i+even[i]<=n and s[i-1-even[i]] == s[i+even[i]])  even[i]++;
		if(even[i] and r<i+even[i]-1) 
		{
			r = i+even[i]-1;
			l = i-even[i];
		}
	}
	h[0] = -1;
	for(int i=1; i<=n; i++)
	{
		h[2*i-1] = odd[i];
		h[2*i] = lcp[i];		
	}
	for(int i=0; i<=2*n; i++)
	{
		while(!st.empty() and h[st.top()]>=h[i])
		{
			int temp = st.top(); st.pop();
			if(temp&1) ans = max(ans, (2*h[temp]-1)*((i%2==1? i-1: i) - (st.top()%2==1? st.top()+1: st.top()))/2);
		 } 
		 st.push(i);
	}
	st = stack<int>();
	for(int i=1; i<=n; i++)
	{
		h[2*i-1] = even[i];
		h[2*i] = lcp[i];
	}
	for(int i=0; i<=2*n; i++)
	{
		while(!st.empty() and h[st.top()]>=h[i])
		{
			int temp = st.top(); st.pop();
			if(temp&1) ans = max(ans, 2*h[temp]*((i%2==1? i-1: i) - (st.top()%2==1? st.top()+1: st.top()))/2);
		}
		st.push(i);
	}
  	assert(ans);
	cout<<ans;
}

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