Submission #107956

#	Time	Username	Problem	Language	Result	Execution time	Memory
107956		SamAnd	Palindromes (APIO14_palindrome)	C++17	8 / 100	1073 ms	22492 KiB

palindrome

#include <bits/stdc++.h>
using namespace std;
const int N = 10004;
const long long P = 31;

int n;
char aa[N], a[N];

long long ast[N];
long long p[N], s[N];

bool pal(int l, int r)
{
    return (p[r] - p[l - 1]) * ast[n - r] == (s[l] - s[r + 1]) * ast[l - 1];
}

unordered_map<long long, int> b[N];

int main()
{
    cin >> aa;
    n = strlen(aa);
    for (int i = 1; i <= n; ++i)
        a[i] = aa[i - 1];

    ast[0] = 1;
    for (int i = 1; i <= n; ++i)
        ast[i] = ast[i - 1] * P;

    for (int i = 1; i <= n; ++i)
        p[i] = p[i - 1] + ast[i - 1] * (a[i] - 'a' + 1);
    for (int i = n; i >= 1; --i)
        s[i] = s[i + 1] + ast[n - i] * (a[i] - 'a' + 1);

    for (int l = 1; l <= n; ++l)
    {
        for (int r = l; r <= n; ++r)
        {
            b[(r - l + 1)][(p[r] - p[l - 1]) * ast[n - r]]++;
        }
    }

    int ans = 0;
    for (int l = 1; l <= n; ++l)
    {
        int pos = 0;
        for (int r = l; r <= n; ++r)
        {
            if (pal(l, r))
                ans = max(ans, b[r - l + 1][(p[r] - p[l - 1]) * ast[n - r]] * (r - l + 1));
        }
    }

    cout << ans << endl;
    return 0;
}

Compilation message (stderr)

palindrome.cpp: In function 'int main()':
palindrome.cpp:46:13: warning: unused variable 'pos' [-Wunused-variable]
         int pos = 0;
             ^~~

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