Submission #418962

#	Time	Username	Problem	Language	Result	Execution time	Memory
418962		Dymo	Palindromes (APIO14_palindrome)	C++14	0 / 100	200 ms	16572 KiB

palindrome

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

#define ll   long long
#define ull unsigned long long
#define ull  long long
#define pll pair<ll,ll>
#define ff first
#define ss second
#define pb push_back
//#define endl "\n"
const ll maxn =1e6+5;
const ll mod=988642507;
const ll base=317;

ull f[maxn];
ull fv[maxn];
ull mu[maxn];
ll n;
ll cntnw=0;
map<ull,ll> mp;
ll cnt[maxn];
ll len[maxn];
ll nxt[maxn];
ll in[maxn];



bool add(ull val,ll len1)
{
    if (!mp.count(val))
    {
        cntnw++;
        len[cntnw]=len1;
        mp[val]=cntnw;
        return true;
    }
    return false;

}

ull get(ll l,ll r)
{
    return ((f[r]-f[l-1]*mu[r-l+1])%mod+mod)%mod;
}
ull getv(ll l,ll r)
{
    swap(l,r);
    l=n-l+1;
    r=n-r+1;
    return ((fv[r]-fv[l-1]*mu[r-l+1])%mod+mod)%mod;
}
bool chk(ll l,ll r)
{
    ll len=(r-l+1)/2;
    if(get(r-len+1,r)==getv(l,l+len-1)) return true;
    return false;
}
int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);

    if (fopen("test.inp","r"))
    {
        freopen("test.inp","r",stdin);
        freopen("test.out","w",stdout);
    }
    mu[0]=1;
    for (int i=1; i<maxn; i++)
        mu[i]=(mu[i-1]*base);
    string s;
    cin>> s;
    string t=s;
    n=s.length();
    s=" "+ s;
    for (int i=1; i<=n; i++)
    {
        f[i]=(f[i-1]*base+s[i]-'a'+1)%mod;
    }
    reverse(t.begin(),t.end());
    t=" "+t;
    for (int i=1; i<=n; i++)
    {
        fv[i]=(fv[i-1]*base+t[i]-'a'+1)%mod;
    }
    ll ans=0;
    for (ll i=1; i<=n; i++)
    {
        ll lenmx=min(i,n-i+1);
        ll l=1,h=lenmx;
        while (l<=h)
        {
            ll mid=(l+h)/2;
            if (chk(i-mid+1,i+mid-1)) l=mid+1;
            else h=mid-1;
        }

      //  if (i==2)cout <<get(2,3)<<" "<<getv(1,2)<<" "<<h<<endl;
     // cout <<i<<" "<<h<<endl;
        ll pre=-1;
        for (int j=h;j>=1;j--)
        {
         //   cout <<j<<endl;
            auto p=add(get(i,i+j-1),j*2-1);
            if (j==h) cnt[mp[get(i,i+j-1)]]++;
            if (pre!=-1) nxt[pre]=mp[get(i,i+j-1)];
            ll t=pre;
            pre=mp[get(i,i+j-1)];
           if (t!=-1) in[pre]++;
            //cout <<mp[get(i,i+j-1)]<<" "<<i<<" "<<i+j-1<<endl;
            if (!p) break;
        }
    }
    queue<ll> q;
   for (int i=1;i<=cntnw;i++)
   {
        if (!in[i]) q.push(i);
   }
 //  cout <<q.size()<<"db"<<endl;
   while (!q.empty())
   {
       auto p=q.front();
       q.pop();
       if (nxt[p]!=0)
       {
           cnt[nxt[p]]+=cnt[p];
           in[nxt[p]]--;
           if (!in[nxt[p]]) q.push(nxt[p]);
       }
       ans=max(ans,cnt[p]*len[p]);
   }
   for (int i=1;i<=cntnw;i++) in[i]=0, len[i]=0, nxt[i]=0, cnt[i]=0;
   cntnw=0;
   mp.clear();
   for (ll i=2; i<=n; i++)
    {
        ll lenmx=min(i-1,n-i+1);
        ll l=1,h=lenmx;
        while (l<=h)
        {
            ll mid=(l+h)/2;
            if (chk(i-mid,i+mid-1)) l=mid+1;
            else h=mid-1;
        }
        ll pre=-1;
        for (int j=h;j>=1;j--)
        {
            auto p=add(get(i,i+j-1),j*2);
            if (j==h) cnt[mp[get(i,i+j-1)]]++;
            if (pre!=-1) nxt[pre]=mp[get(i,i+j-1)];
            ll t=pre;
            pre=mp[get(i,i+j-1)];
            if (t!=-1) in[pre]++;
            if (!p) break;
        }
    }
   for (int i=1;i<=cntnw;i++)
   {
        if (!in[i]) q.push(i);
   }
   while (!q.empty())
   {
       auto p=q.front();
       q.pop();
       if (nxt[p]!=0)
       {
           cnt[nxt[p]]+=cnt[p];
           in[nxt[p]]--;
           if (!in[nxt[p]]) q.push(nxt[p]);
       }
       ans=max(ans,cnt[p]*len[p]);
   }
   cout <<ans;


}

Compilation message (stderr)

palindrome.cpp:6: warning: "ull" redefined
    6 | #define ull  long long
      | 
palindrome.cpp:5: note: this is the location of the previous definition
    5 | #define ull unsigned long long
      | 
palindrome.cpp: In function 'int main()':
palindrome.cpp:66:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |         freopen("test.inp","r",stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~
palindrome.cpp:67:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   67 |         freopen("test.out","w",stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~

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