Palindrome Check Go
Fast recall
Quick revision
Core answer
Whether you understand Palindrome Check Go beyond memorized syntax.
Giving a definition without explaining a practical trade-off.
Connect the concept to a small production example and state its complexity or failure mode.
Interview-ready guide
Interview answer
The two-pointer solution, executed:
func isPalindrome(s string) bool {
for i, j := 0, len(s)-1; i < j; i, j = i+1, j-1 {
if s[i] != s[j] {
return false
}
}
return true
}
// isPalindrome("racecar") → true — verified
// isPalindrome("hello") → false — verifiedThe mechanics: i from the start, j from the end, moving toward each other. Each step compares the pair. The first mismatch returns false immediately — no need to check further. The loop ends (i >= j) on a confirmed palindrome.
The invariants: everything before i and after j is already confirmed; s[i..j] is the unchecked remainder. Each iteration either finds a mismatch (done) or shrinks the range by 2.
The variants that upgrade the question:
- Case-insensitive: strings.ToLower both sides first
- Ignoring non-alphanumerics (the "A man, a plan, a canal: Panama" case): skip or filter
- Multi-word/phrase palindromes: normalize, strip punctuation, then the same two-pointer
The complexity: O(n) time (n/2 comparisons), O(1) space (two indices — no copy, no allocation). The alternative — reverse and compare — is O(n) space for the reversed copy; two-pointer is strictly better.
Palindrome Check Go
Direct Answer
Two-pointer: compare s[i] and s[j] from both ends, advance inward. First mismatch = false. O(n) time, O(1) space. Verified: "racecar" true, "hello" false.
Deep Dive & Architecture
The rune-safe version, for the interview completeness: the byte-indexed loop works for ASCII; a multibyte string needs rune-based access (the DSA topic's reverse insight). The safe pattern: convert to []rune, two-pointer over the rune slice, compare — the same O(n)/O(n-for-conversion) as any Unicode handling.
The two-pointer's early exit, quantified: a palindrome check on a string that fails at position 0 returns after ONE comparison — the algorithm's best case is O(1). The reverse-and-compare always does the full O(n) reverse. The performance folklore: two-pointer's early exit matters on adversarial input (random strings that rarely are palindromes — the common case for a filter).
The circular palindrome / longest-substring-palindrome extensions (Manacher's algorithm, expand-around-center) — the two-pointer base case is the primitive those build on. The interview flow: two-pointer first (correct, optimal), the extensions if the role is algorithm-heavy.
Common Mistakes & Pitfalls
Giving a definition without explaining a practical trade-off.
Check your understanding
Answer these without looking back at the article.
- When would you use Palindrome Check Go in a real project?
- How would you compare Palindrome Check Go with an alternative?
- What is a common mistake when using Palindrome Check Go?
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