📅 Date: Jan 28, 2026
🔥 Topic: Logic Building: Palindrome Check

🤔 What is a Palindrome?

A palindrome is a word, number, or phrase that reads the same backwards as forwards.

  • Valid: MOM, RACECAR, MADAM, 121
  • Invalid: HELLO, 123

💡 The Two-Pointer Approach

Instead of reversing the whole string (which uses extra memory), I used the Two-Pointer Technique.

  1. Put one finger (pointer) at the Start.
  2. Put one finger at the End.
  3. Compare them. If they match, move start forward and end backward.
  4. If they don't match at any point -> Not a Palindrome.

💻 Day 28 Code

#include <iostream>
#include <string>
using namespace std;

int main() {
    string s;
    cout << "Enter string: ";
    cin >> s;

    int start = 0;
    int end = s.length() - 1;
    bool isPalindrome = true;

    while(start < end) {
        if(s[start] != s[end]) {
            isPalindrome = false;
            break; // Stop checking
        }
        start++;
        end--;
    }

    if(isPalindrome)
        cout << "Yes! It is a Palindrome." << endl;
    else
        cout << "No. Not a Palindrome." << endl;

    return 0;
}

💭 Thoughts

This logic is O(n/2), which is O(n) Time Complexity. It's efficient. The two-pointer pattern is something I'll definitely see again in DSA.