✌🏻 Sum

Two Sum Problem: The Ultimate Dating App Algorithm 💕

The Story

• Imagine you’re a matchmaker for numbers! Your job is to find two numbers in an array that add up to a target value. It’s like Tinder, but for math.

The Drama 🎬

• Naive Approach : Let me check for EVERY possible pair! O(n²) complexity enters the chat 😱
• Smart Approach : I will use a Map as my little black book! O(n) complexity winks 😎

The Algorithm (aka “The Wingman Strategy”)

• Meet and Greet : Walk through the array one number at a time.
• Calculate Compatibility : For each number, calculate what its “perfect match” would be (target - curr_number)
• Check Your Contacts : Look into your Map to see if you’ve already met this perfect match.
• Match Found : If yes, return both indices and play Cupid 💘
• Add to Contacts : If no, add current number to your Map and keep searching.

The Punchline 🤡

// Before: "I need to check everyone with everyone!"
// After: "I remember everyone I've met, so I only need one pass!"

Fun Fact

• Your solution return [-1, -1] if no pair found, which is like saying, “Sorry, no match found on this dating app!”

Memory Palace 🧠

• Map = Your contact list (remember who you’ve seen)
• diff = The Perfect partner you were looking for!
• One pass = Speed dating efficiency!

Complexity : O(n) time and O(n) space - because being efficient is sexy! ✨

The Actual Code (Your Masterpiece) 🎨

    const twoSum = (nums, target) => {
        let map = new Map()
        for(let i =0; i<nums.length; i++){
            let diff = target - nums[i]
            if(map.has(diff)){
                return [map.get(diff), i]
            }
            map.set(nums[i], i)
        }
        return [-1, -1]
    }

Test Drive 🚗

// Example: nums = [2,7,11,15], target = 9
// Step 1: See 2, looking for 7, don't have 7 yet → save 2
// Step 2: See 7, looking for 2, found 2 at index 0! → return [0,1] 🎯