Find First Palindromic String in the Array

Find First Palindromic String in the Array

What is this problem about?

The Find First Palindromic String in the Array coding problem asks you to iterate through a list of strings and return the very first one that reads the same forwards and backwards. If no such string exists, you return an empty string. It’s a straightforward combination of array traversal and string validation.

Why is this asked in interviews?

Companies like Amazon and Bloomberg use this Find First Palindromic String in the Array interview question as an early-round screening task. It checks basic Array and String interview pattern proficiency. It evaluates whether you can write clean code, handle edge cases (like single-character strings), and implement a simple validation helper without introducing unnecessary complexity or overhead.

Algorithmic pattern used

The problem uses a Linear Scan combined with the Two Pointers interview pattern.

1. Iterate through the array from left to right.
2. For each string, check if it's a palindrome by placing one pointer at the start and one at the end.
3. Compare characters while moving the pointers toward the middle. If all pairs match, the string is a palindrome.
4. Return the first string that passes this test.

Example explanation

Array: ["abc", "car", "ada", "racecar", "cool"]

1. Check "abc": 'a' != 'c'. Not a palindrome.
2. Check "car": 'c' != 'r'. Not a palindrome.
3. Check "ada": 'a' == 'a'. Midpoint reached. Palindrome found! Result: "ada". Note that even though "racecar" is also a palindrome, "ada" appeared first.

Common mistakes candidates make

• Inefficient Reversal: Checking for palindromes by creating a reversed copy of every string (s == s[::-1]). While concise, this creates extra objects in memory. The two-pointer approach is more efficient.
• Wait for completion: Continuing to scan the array even after the first palindrome is found. The problem asks for the first one, so you should return immediately.
• Case Sensitivity: Not checking if the strings are all lowercase or if they contain special characters (though usually, the problem specifies lowercase English letters).

Interview preparation tip

Always implement a separate isPalindrome helper function. It makes your main loop cleaner and follows the "Single Responsibility Principle," which interviewers appreciate.