Submission #299095

#	Time	Username	Problem	Language	Result	Execution time	Memory
299095		AaronNaidu	Palindromes (APIO14_palindrome)	C++14	0 / 100	1091 ms	2588 KiB

palindrome

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

ll mod1 = 1000000007;
ll mod2 = 1000000009;
string s;
ll n;
ll prefSums[20000], sufSums[20000];
ll pows[20000];
unordered_map<ll, ll> m;
int main() {
    cin >> s;
    ll thisPow = 1;
    n = s.length();
    for (int i = 0; i < n; i++)
    {
        pows[i]= thisPow;
        thisPow *= 11;
        thisPow %= mod1;
    }
    prefSums[0] = s[0] - 'a' + 1;
    for (int i = 1; i < n; i++)
    {
        prefSums[i] = prefSums[i-1] + (s[i] - 'a' + 1) * pows[i];  
        prefSums[i] %= mod1;  
    }
    sufSums[n-1] = s[n-1] - 'a' + 1;
    for (int i = n-2; i >= 0; i--)
    {
        sufSums[i] = sufSums[i+1] + (s[i] - 'a' + 1) * pows[n-1-i];
        sufSums[i] %= mod1;
    }
    /*for (int j = 0; j < n; j++)
    {
        cout << prefSums[j] << " ";
        //cout << prefSums[j] << " " << sufSums[j] << "\n";
    }
    cout << "\n";
    for (int i = 1; i < n; i++)
    {
        for (int j = i; j < n; j++)
        {
            cout << (prefSums[j] - prefSums[i-1]) / pows[i] << " ";
        }
        cout << "\n";
    }
    cout << "\n";
    for (int i = 0; i < n; i++)
    {
        for (int j = i; j < n-1; j++)
        {
            cout << (sufSums[i] - sufSums[j+1]) / pows[n-1-j] << " ";
        }
        cout << sufSums[i];
        cout << "\n";
    }*/
    ll totMax = 0;
    for (int j = 0; j < n-1; j++)
    {
        if (prefSums[j] == (sufSums[0]-sufSums[j+1])/pows[n-1-j])
        {
            ll curr = 0;
            if (m.find(prefSums[j]) != m.end())
            {
                curr = m.find(prefSums[j])->second;
                m.erase(prefSums[j]);
            }
            curr += j+1;
            totMax = max(totMax, curr);
            m.insert({prefSums[j], curr});
        }
    }
    if (prefSums[n-1] == sufSums[0])
    {
        ll curr = 0;
        if (m.find(prefSums[n-1]) != m.end())
        {
            curr = m.find(prefSums[n-1])->second;
            m.erase(prefSums[n-1]);
        }
        curr += n;
        totMax = max(totMax, curr);
        m.insert({prefSums[n-1], curr});
    }
    for (int i = 1; i < n; i++)
    {
        for (int j = i; j < n-1; j++)
        {
            if ((prefSums[j]-prefSums[i-1])/pows[i] == (sufSums[i]-sufSums[j+1])/pows[n-1-j])
            {
                ll curr = 0;
                if (m.find((prefSums[j]-prefSums[i-1])/pows[i]) != m.end())
                {
                    curr = m.find((prefSums[j]-prefSums[i-1])/pows[i])->second;
                    m.erase((prefSums[j]-prefSums[i-1])/pows[i]);
                }
                curr += j-i+1;
                totMax = max(totMax, curr);
                m.insert({(prefSums[j]-prefSums[i-1])/pows[i], curr});
            }
        }
        if ((prefSums[n-1]-prefSums[i-1])/pows[i] == sufSums[i])
        {
            ll curr = 0;
            if (m.find(sufSums[i]) != m.end())
            {
                curr = m.find(sufSums[i])->second;
                m.erase(sufSums[i]);
            }
            curr += n-i;
            totMax = max(totMax, curr);
            m.insert({sufSums[i], curr});
        }
    }
    cout << totMax << "\n";
}

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