LeetCode 121 | Best Time to Buy & Sell Stock | O(n²) Brute Force to Optimal O(n) | Interview

LeetCode 121 Solution – Best Time to Buy and Sell Stock | Brute Force O(n²) to Optimal O(n) In this video, I explain LeetCode 121: Best Time to Buy and Sell Stock step by step, starting with the Brute Force O(n²) approach and then optimizing it to the Optimal O(n) solution. If you are searching for LeetCode 121 solution, Best Time to Buy and Sell Stock explanation, LeetCode 121 optimal solution, LeetCode 121 brute force approach, or an important DSA interview question, this video walks through the complete problem-solving process from basic intuition to an efficient one-pass solution. We first understand the problem using the example and explore the brute-force approach where different buy and sell combinations are checked. Then we identify the key observation that allows us to reduce the time complexity from O(n²) to O(n). In the optimal approach, we keep track of the minimum stock price seen so far and calculate the maximum possible profit while traversing the array only once. This problem is useful for understanding: ✅ LeetCode 121 – Best Time to Buy and Sell Stock ✅ Brute Force O(n²) approach ✅ Optimal O(n) one-pass solution ✅ Array traversal ✅ Minimum price tracking ✅ Maximum profit calculation ✅ Time and space complexity ✅ How to optimize brute-force solutions ✅ DSA problem-solving patterns ✅ Coding interview preparation ✅ Software engineering interview questions ✅ LeetCode array problems This is a useful problem for anyone preparing for DSA interviews, coding interviews, software engineering interviews, placement coding rounds, technical interviews, or practicing LeetCode problems. 📌 Chapters: 00:00 Problem Statement & Example 03:50 Brute Force Approach O(n²) 09:40 Optimal Approach O(n) 16:04 Brute Force Solution in LeetCode Editor 19:25 Optimal O(n) Solution in LeetCode Editor Problem: LeetCode 121 – Best Time to Buy and Sell Stock Difficulty: Easy Topic: Array Brute Force Time Complexity: O(n²) Optimal Time Complexity: O(n) The main learning from this problem is how to move from checking every possible buy-and-sell pair to solving the same problem efficiently in just one pass through the array. If you are learning Data Structures and Algorithms, try solving the problem yourself before watching the optimal solution. Understanding how the brute-force approach evolves into the optimized approach is an important skill for coding interviews. Keep Learning, Keep Growing 🚀 If this video helped you, like the video, subscribe for more LeetCode solutions, DSA problems, algorithms, coding interview questions, and problem-solving tutorials. Comment below which LeetCode problem you want me to solve next. #LeetCode121 #BestTimeToBuyAndSellStock #LeetCode #DSA #CodingInterview #Algorithms #DataStructures #ProblemSolving #InterviewPreparation #ArrayProblems #LeetCodeSolution