Day 7 of My DSA Problem Solving Journey (JavaScript Edition) 🚀

Today, I tackled two foundational and frequently asked coding interview problems — Two Sum and Palindrome Number — both great for strengthening your problem-solving skills in JavaScript. I focused on writing clean code, understanding constraints, dry running inputs, and thinking through edge cases.

✅ Problem 1: Two Sum

📝 Problem Statement:

• Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.

• You may assume that each input would have exactly one solution, and you may not use the same element twice.

• Return the answer in any order.

Example

Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
// Explanation: Because nums[0] + nums[1] == 9

✅ JavaScript Code:

var twoSum = function(nums, target) {   
    if(nums.length < 2) return null;

    for(let i = 0; i < nums.length; i++) {
        for(let j = i + 1; j < nums.length; j++) {
            if(nums[i] + nums[j] === target) {
                return [i, j];
            }
        }
    }
};

// Testing the function
console.log('First Answer', twoSum([2, 7, 11, 15], 9));   // [0,1]
console.log('Second Answer', twoSum([3, 2, 4], 6));       // [1,2]
console.log('Third Answer', twoSum([3, 3], 6));           // [0,1]
console.log('Fourth Answer', twoSum([3, 2, 3], 6));       // [0,2]

✅ Problem 2: Palindrome Number

📝 Problem Statement:

• Given an integer x, return true if x is a palindrome, and false otherwise.

Example

Input: x = 121
Output: true

Input: x = -121
Output: false

Input: x = 10
Output: false

✅ JavaScript Code:

var isPalindrome = function(x) {
    let ActualValue = x.toString();
    let ReverseValue = x.toString().split('').reverse().join('');
    console.log(ActualValue, ReverseValue);

    return ActualValue === ReverseValue;
};

// Testing the function
console.log(isPalindrome(121));   // true
console.log(isPalindrome(-121));  // false
console.log(isPalindrome(10));    // false

🔁 What I Learned Today

🧠 1. Dry Run Is Powerful

Manually walking through the logic before coding saved time and reduced bugs.

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🧩 2. Think About Edge Cases

I considered inputs like:

• Arrays with one element
• Duplicate values
• Negative integers

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🧼 3. Clean Code Matters

Writing clean and readable code helps future-proof my logic and reduces confusion.

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⚙️ 4. Brute Force is OK at First

Start with what's simple and correct. Optimization can come later once the logic is solid.

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✍️ 5. "Copy & Think" Habit

Instead of copy-pasting code, I pause to understand why it works. This makes learning deeper and longer-lasting.