# Check if an array has some palindromic subsequence of length at least 3

Given is an array Arr of integers. The task is to determine if the array has any subsequence of at least length 3 that is a palindrome.

Examples:

```Input: Arr[] = [1, 2, 1]
Output: YES
Explanation:
Here 1 2 1 is a palindrome.

Input: Arr[] = [1, 1, 2, 2, 3, 3, 4, 4, 5, 5]
Output: NO
Explanation:
Here no subsequence of length at least 3
exists which is a palindrome.
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

Approach:

• The idea is to check only for length 3 because if a palindromic subsequence of length greater than 3 exists then there is always a palindromic subsequence of length 3.
• To find the palindromic subsequence of length 3 we just need to find a pair of equal non-adjacent number.

Below is the implementation of the above approach:

## C++

 `// C++ code to check if  ` `// palindromic subsequece of ` `// length atleast 3 exist or not ` `#include ` `using` `namespace` `std; ` ` `  `string SubPalindrome(``int` `n, ``int` `arr[]) ` `{ ` `    ``bool` `ok = ``false``; ` `    ``for` `(``int` `i = 0; i < n; i++) ` `    ``{ ` `        ``for``(``int` `j = i + 2; j < n; j++) ` `        ``{  ` `            ``if``(arr[i] == arr[j]) ` `                ``ok = ``true``; ` `        ``} ` `    ``} ` `    ``if``(ok) ` `        ``return` `"YES"``; ` `    ``else` `        ``return` `"NO"``; ` `} ` `     `  ` `  `// Driver code ` `int` `main() ` `{ ` ` `  `    ``// Input values to list ` `    ``int` `Arr[] = {1, 2, 2, 3, 2}; ` `     `  `    ``// Calculating length of array  ` `    ``int` `N = ``sizeof``(Arr)/``sizeof``(Arr); ` `     `  `    ``cout << SubPalindrome(N, Arr); ` `} ` ` `  `// This code is contributed by Bhupendra_Singh `

## Java

 `// Java code to check if  ` `// palindromic subsequece of ` `// length atleast 3 exist or not ` ` `  `import` `java.util.*; ` ` `  `class` `GFG{ ` `  `  `static` `String SubPalindrome(``int` `n, ``int` `arr[]) ` `{ ` `    ``boolean` `ok = ``false``; ` `    ``for` `(``int` `i = ``0``; i < n; i++) ` `    ``{ ` `        ``for``(``int` `j = i + ``2``; j < n; j++) ` `        ``{  ` `            ``if``(arr[i] == arr[j]) ` `                ``ok = ``true``; ` `        ``} ` `    ``} ` `    ``if``(ok) ` `        ``return` `"YES"``; ` `    ``else` `        ``return` `"NO"``; ` `} ` `      `  `  `  `// Driver code ` `public` `static` `void` `main(String[] args) ` `{ ` `  `  `    ``// Input values to list ` `    ``int` `Arr[] = {``1``, ``2``, ``2``, ``3``, ``2``}; ` `      `  `    ``// Calculating length of array  ` `    ``int` `N = Arr.length; ` `      `  `    ``System.out.print(SubPalindrome(N, Arr)); ` `} ` `} ` ` `  `// This code contributed by sapnasingh4991 `

## Python3

 `# Python 3 code to check if  ` `# palindromic subsequece of ` `# length atleast 3 exist or not ` `def` `SubPalindrome (n, arr): ` `    ``ok ``=` `False` `    ``for` `i ``in` `range``(n): ` `        ``for` `j ``in` `range``(i ``+` `2``, n): ` `            ``if` `arr[i] ``=``=` `arr[j]: ` `                ``ok ``=` `True` `    ``return``(``'YES'` `if` `ok ``else` `'NO'``) ` ` `  `# Driver code ` ` `  `# Input values to list ` `Arr ``=` `[``1``, ``2``, ``2``, ``3``, ``2``] ` ` `  `# Calculating length of the array  ` `N ``=` `len``(arr) ` ` `  `print` `(SubPalindrome(N, Arr)) `

## C#

 `// C# code to check if  ` `// palindromic subsequece of ` `// length atleast 3 exist or not ` `using` `System; ` ` `  `public` `class` `GFG{ ` ` `  `static` `string` `SubPalindrome(``int` `n, ``int` `[]arr) ` `{ ` `    ``bool` `ok = ``false``; ` `    ``for``(``int` `i = 0; i < n; i++) ` `    ``{ ` `        ``for``(``int` `j = i + 2; j < n; j++) ` `        ``{  ` `            ``if``(arr[i] == arr[j]) ` `                ``ok = ``true``; ` `        ``} ` `    ``} ` `    ``if``(ok) ` `        ``return` `"YES"``; ` `    ``else` `        ``return` `"NO"``; ` `} ` `     `  `// Driver code ` `static` `public` `void` `Main () ` `{ ` `    ``// Input values to list ` `    ``int` `[]Arr = { 1, 2, 2, 3, 2 }; ` `     `  `    ``// Calculating length of array  ` `    ``int` `N = Arr.Length; ` `    ``Console.WriteLine(SubPalindrome(N, Arr)); ` `} ` `} ` ` `  `// This code is contributed by shivanisinghss2110 `

Output:

```YES
```

Time Complexity:O(N^2) My Personal Notes arrow_drop_up Check out this Author's contributed articles.

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