Two Sum LeetCode Solution

🚀 50 Important Coding Questions – Question 27/50 🔹 Sort List | LeetCode (Medium) A very important Linked List problem that teaches sorting using Merge Sort 📚 📌 Problem Statement Given the head of a linked list, sort it in ascending order. 💡 Optimal Approach – Merge Sort on Linked List Why Merge Sort? Because Linked Lists don’t support random access like arrays. 👉 Steps 1️⃣ Find middle of list using slow & fast pointers 2️⃣ Split list into two halves 3️⃣ Recursively sort both halves 4️⃣ Merge sorted lists 🧠 Why this problem is important? ✔ Teaches Merge Sort logic ✔ Important interview question ✔ Helps in advanced Linked List problems ✔ Improves recursion understanding ⏱ Time Complexity: O(n log n) 📦 Space Complexity: O(log n) (recursion stack) 👉 My approach used array conversion + sorting, but Merge Sort is the optimal in interviews. 📌 LeetCode Result: ✔ Accepted ⚡ Efficient solution 🔔 This is Question 27 of my “50 Important Coding Questions” series. Linked List concepts getting stronger 💪 👉 Question 28 coming soon… #DSA #LeetCode #LinkedList #MergeSort #CodingInterview #CPlusPlus #ProblemSolving #50ImportantQuestions

🚀 50 Important Coding Questions – Question 6/50 🔹 Subarray Sum Equals K | LeetCode (Medium) A powerful combination of Prefix Sum + Hash Map that appears very frequently in coding interviews 👇 📌 Problem Statement Given an integer array nums and an integer k, return the total number of continuous subarrays whose sum equals k. 💡 Optimized Approach (Prefix Sum + Hashing) Maintain a running prefix sum For each index, check if 👉 (currentPrefixSum − k) exists in the map Count how many times it has appeared ⏱ Time Complexity: O(n) 📦 Space Complexity: O(n) ✅ Why this problem is important? ✔ Classic example of Prefix Sum with Hash Map ✔ Works even with negative numbers ✔ Asked frequently in FAANG & product-based interviews ✔ Builds intuition for subarray counting problems 📌 LeetCode Result: ✔ Accepted ⚡ Optimized & interview-ready solution 🔔 This is Question 6 of my “50 Important Coding Questions” series. Follow for daily DSA problems, optimized approaches, and clean C++ solutions 💻✨ 👉 Question 7 coming soon… #DSA #LeetCode #SubarraySumEqualsK #PrefixSum #HashMap #CPlusPlus #CodingInterview #50ImportantQuestions

🚀 50 Important Coding Questions – Question 2/50 🔹 Rotate Array | LeetCode (Medium) Another classic interview problem that tests your array manipulation & in-place logic 👇 📌 Problem Statement Given an integer array nums, rotate the array to the right by k steps, where k is non-negative. 💡 Optimized Approach (Reverse Technique) Instead of rotating one-by-one, use 3 reversals: 1️⃣ Reverse the entire array 2️⃣ Reverse the first k elements 3️⃣ Reverse the remaining elements ⏱ Time Complexity: O(n) 📦 Space Complexity: O(1) (In-place) ✅ Why this problem is important? ✔ Teaches in-place array manipulation ✔ Avoids extra memory usage ✔ Frequently asked in FAANG interviews ✔ Builds intuition for rotation & reversal logic 📌 LeetCode Result: ✔ Accepted ⚡ Runtime: 0 ms (Beats 100%) 📊 Memory Efficient 🔔 This is Question 2 of my “50 Important Coding Questions” series. Follow for daily DSA problems, optimized solutions, and interview-ready logic 💻✨ 👉 Question 3 coming soon… #DSA #LeetCode #RotateArray #CPlusPlus #CodingInterview #Arrays #ProblemSolving #50ImportantQuestions #TopInterview150

🚀 50 Important Coding Questions – Question 21/50 🔹 Reverse Linked List | LeetCode (Easy) A core Linked List problem that every coding interview candidate must master 👇 📌 Problem Statement Given the head of a singly linked list, reverse the list and return the new head. 💡 Optimized Approach (Iterative – Three Pointers) Use three pointers: 👉 prev → previous node 👉 curr → current node 👉 next → next node Steps: 1️⃣ Store next node 2️⃣ Reverse current pointer 3️⃣ Move pointers forward ⏱ Time Complexity: O(n) 📦 Space Complexity: O(1) ✅ Why this problem is important? ✔ Foundation for all Linked List problems ✔ Tests pointer manipulation skills ✔ Frequently asked in interviews ✔ Needed for problems like Reverse in K-groups, Palindrome Linked List 📌 LeetCode Result: ✔ Accepted ⚡ Runtime: 0 ms (Beats 100%) 📊 Memory Efficient 🔔 This is Question 21 of my “50 Important Coding Questions” series. Linked Lists unlocked 🔓 Keep going 💪 👉 Question 22 coming soon… #DSA #LeetCode #ReverseLinkedList #LinkedList #Pointers #CPlusPlus #CodingInterview #ProblemSolving #50ImportantQuestions

🚀 50 Important Coding Questions – Question 9/50 🔹 Find First and Last Position of Element in Sorted Array | LeetCode (Medium) A classic Binary Search variation that tests how well you understand search boundaries 👇 📌 Problem Statement Given a sorted array of integers and a target value, find the starting and ending position of the target. If the target is not found, return [-1, -1]. 💡 Optimized Approach (Modified Binary Search) Use binary search twice First pass → find the first occurrence Second pass → find the last occurrence Narrow search space even after finding the target ⏱ Time Complexity: O(log n) 📦 Space Complexity: O(1) ✅ Why this problem is important? ✔ Strengthens binary search mastery ✔ Introduces boundary-based searching ✔ Very common in FAANG & product-based interviews ✔ Foundation for lower/upper bound problems 📌 LeetCode Result: ✔ Accepted ⚡ Runtime: 0 ms (Beats 100%) 📊 Memory Efficient 🔔 This is Question 9 of my “50 Important Coding Questions” series. Follow for daily DSA problems, optimized approaches, and interview-ready logic 💻✨ 👉 Question 10 coming soon… #DSA #LeetCode #BinarySearch #Arrays #CPlusPlus #CodingInterview #ProblemSolving #50ImportantQuestions

You don’t need 500 LeetCode problems. You need the right 150. Because ~90% of coding interviews are variations of a small set of patterns: ✓ Two Pointers ✓ Sliding Window ✓ Binary Search ✓ DFS / BFS ✓ Dynamic Programming ✓ Backtracking ✓ Fast & Slow Pointers ✓ Merge Intervals ✓ Top K ✓ Tree Traversals 🎯 A smarter way to prepare For each pattern: • Understand the idea (30 mins) • Solve 3 easy → recognize it • Solve 3 medium → build muscle • Solve 1 hard → push limits • Write a template / cheatsheet → Move on. Why this works 👇 When a new question appears, your brain thinks: “I’ve seen this pattern before.” Not: “Where do I even begin?” 📌 Truth most people learn late: Pattern mastery = 80% of success Fancy tricks = 20% 👉 Follow Ritik Jain for practical interview prep, DSA strategy, and engineering career tips. #DSA #LeetCode #CodingInterview #SoftwareEngineer #TechCareers #ProblemSolving #Algorithms #InterviewPrep #Developers #LearnToCode

The LeetCode 2026 Strategy Guide: 🟢 Easy: Arrays, Strings, Linked Lists (The Foundation) 🟡 Medium: Trees, Graphs, Dynamic Programming (The Differentiators) 🔴 Hard: Advanced Graphs, Segment Trees (The Senior Level) This post organizes the chaos into a clear, topic-wise plan. Check it out and start your grind today! 🚀

𝗟𝗲𝗲𝘁𝗖𝗼𝗱𝗲 𝗤𝘂𝗲𝘀𝘁𝗶𝗼𝗻𝘀 𝗳𝗼𝗿 𝗗𝗲𝘃𝗲𝗹𝗼𝗽𝗲𝗿𝘀 – 𝗠𝗮𝘀𝘁𝗲𝗿 𝗖𝗼𝗱𝗶𝗻𝗴 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝘀 𝘄𝗶𝘁𝗵 𝗣𝗿𝗮𝗰𝘁𝗶𝗰𝗲 𝗣𝗿𝗼𝗯𝗹𝗲𝗺𝘀 Boost your problem-solving skills with essential LeetCode questions every developer should practice. This guide covers popular coding problems from arrays, strings, linked lists, stacks, queues, trees, graphs, recursion, and dynamic programming. Perfect for developers preparing for technical interviews at top tech companies. Improve your logic, coding speed, and confidence by practicing real interview-level problems with structured learning. #LeetCode #CodingInterview #DSA #ProblemSolving #SoftwareEngineering #ProgrammingPractice #TechInterviews #Developers #Algorithms #DataStructures #InterviewPreparation #CodeWithGandhi

I used to think solving LeetCode problems was enough. I solved the problem. The code passed. I moved on. Then interviews exposed the gap. “Why this approach?” “What’s the time complexity?” “Can you optimize this?” “What breaks at scale?” That’s when I realized 👇 Solutions matter more than answers. So I started documenting clear, optimized LeetCode solutions — not just code, but thinking. What these solutions focus on: ✅ Brute force → optimized approach ✅ Time & space complexity explained ✅ Patterns behind the problems ✅ Why one solution is better than another Perfect if you’re: 🎯 Preparing for coding interviews 🎯 Struggling to explain your logic 🎯 Tired of memorizing without understanding Because interviews don’t reward speed alone — they reward clarity of thought. 👉 Follow #thevinia for DSA, system design, and real interview prep. #LeetCode #DSA #CodingInterviews #ProblemSolving #SoftwareEngineer #InterviewPreparation

🚀 LeetCode Challenge: [🔥Day 859] 🔍 Problem Title: ❓Prime Number of Set Bits in Binary Representation 📝 Description: 🤯Given two integers left and right, return the count of numbers in the inclusive range [left, right] having a prime number of set bits in their binary representation. Recall that the number of set bits an integer has is the number of 1's present when written in binary. For example, 21 written in binary is 10101, which has 3 set bits.   Example 1: Input: left = 6, right = 10 Output: 4 Explanation: 6 -> 110 (2 set bits, 2 is prime) 7 -> 111 (3 set bits, 3 is prime) 8 -> 1000 (1 set bit, 1 is not prime) 9 -> 1001 (2 set bits, 2 is prime) 10 -> 1010 (2 set bits, 2 is prime) 4 numbers have a prime number of set bits. Example 2: Input: left = 10, right = 15 Output: 5 Explanation: 10 -> 1010 (2 set bits, 2 is prime) 11 -> 1011 (3 set bits, 3 is prime) 12 -> 1100 (2 set bits, 2 is prime) 13 -> 1101 (3 set bits, 3 is prime) 14 -> 1110 (3 set bits, 3 is prime) 15 -> 1111 (4 set bits, 4 is not prime) 5 numbers have a prime number of set bits.   Constraints: 1 <= left <= right <= 106 0 <= right - left <= 104 Link to Problem: https://lnkd.in/d7dt2qYm ✨ Why this Challenge is Worth Your Time: Sharpen your problem-solving skills. Enhance your algorithmic understanding. Perfect for interview preparation! #DSA #leetcode #SDE