Check Palindrome
Check if a string is a palindrome.
Palindrome detection is a fundamental algorithmic problem that teaches string comparison, reversal techniques, and optimization strategies. This exercise will help you master string manipulation while understanding different algorithmic approaches.
📚 Concepts & Theory
A palindrome is a word, phrase, or sequence that reads the same backward as forward, like "racecar" or "madam". Checking for palindromes is a classic string manipulation problem that combines string reversal with comparison logic.
Understanding Palindrome Logic:
- Compare the string with its reverse
- If they match, it's a palindrome
- Case sensitivity matters: "Racecar" ≠ "racecaR"
def is_palindrome(text):
return text == text[::-1]Approach 2: Two-Pointer Technique
Compare characters from both ends moving inward:
def is_palindrome(text):
left, right = 0, len(text) - 1
while left < right:
if text[left] != text[right]:
return False
left += 1
right -= 1
return TrueApproach 3: Using reversed()
def is_palindrome(text):
return list(text) == list(reversed(text))The two-pointer technique is more space-efficient as it doesn't create a reversed copy. For case-insensitive checking, convert to lowercase first: text.lower().
🎯 Your Challenge
Write is_palindrome that returns True/False.
📝 Starter Code
def is_palindrome(text):
pass
print(is_palindrome('radar'))- A palindrome reads the same forwards and backwards
- Try reversing the string and comparing
- The [::-1] slice can reverse a string
- Don't forget: empty strings and single characters are palindromes
Solution
def is_palindrome(text):
text = text.lower().replace(' ', '')
return text == text[::-1]
print(is_palindrome('radar'))Explanation
This solution compares the original string with its reversed version using Python's slicing syntax [::-1]. If they are identical, the string reads the same forwards and backwards, making it a palindrome. This is the most concise and Pythonic approach. Time complexity: O(n) for creating the reversed string and O(n) for comparison, total O(n). Space complexity: O(n) for storing the reversed string.
⚠️ Common Mistakes to Avoid
- Not handling case sensitivity ("Racecar" vs "racecar")
- Forgetting to handle spaces in phrases ("race car")
- Comparing with wrong direction (result + char)
- Not considering empty strings (which are palindromes)