Core Concept Mastery • DSA Module
Common string problems in interviews include palindrome checks, reversing strings, and anagram detection. These test your understanding of two-pointer techniques and character frequency counting.
Palindrome: 'RACECAR' reads the same forwards and backwards. Reverse: 'HELLO' becomes 'OLLEH'. Anagram: 'LISTEN' and 'SILENT' have the same letters in different orders.
"RACECAR" forwards is "RACECAR" backwards.
Use two pointers moving inward, comparing characters.
"HELLO" → "OLLEH". Usually done with Two Pointers.
Swap characters from both ends moving inward.
"LISTEN" and "SILENT". Same letters, different order.
Count character frequencies and compare.
Ready
String 1: "LISTEN"
String 2: "SILENT"
Ready
1bool isPalindrome(string s) {2int left = 0;3int right = s.length() - 1;4while (left < right) {6if (s[left] != s[right]) {7return false; // Mismatch found8}9left++;10right--;11}12return true; // All characters matched13}14// Time: O(n), Space: O(1)
1void reverseString(char* s, int length) {2int left = 0;3int right = length - 1;4while (left < right) {6// Swap characters7char temp = s[left];8s[left] = s[right];9s[right] = temp;10left++;12right--;13}14}15// Time: O(n), Space: O(1)
Let's solve these step by step.
1. Palindrome Check
A palindrome reads the same forwards and backwards:
Solution: Two Pointers
2. Reverse String
Flip the string: "HELLO" → "OLLEH"
Solution: Two Pointers Swap
3. Anagram Check
Two strings have same letters, different order:
Solution: Character Frequency
Key Techniques
These problems appear in almost every coding interview. Mastering them builds your problem-solving skills and demonstrates your understanding of string manipulation techniques.
"How do you check if a string is a palindrome?"
Use two pointers: one at the start and one at the end. Compare characters while moving pointers inward. If all characters match, it's a palindrome. Time complexity is O(n).