Fast And Slow Pointer. In this comprehensive guide, we’ll dive deep into the fast an
In this comprehensive guide, we’ll dive deep into the fast and slow pointers technique, exploring its applications, implementation, and how it can give you an edge in coding interviews. pdf from CS 400 at Anna University, Chennai. 馃 Key Learnings Day 27 Problem solving on leetcode 1Day = 1 Question on leetcode 馃憤 馃憤 馃殌 LeetCode 876 | Middle of the Linked List This problem is a classic example of using the fast and slow pointer 馃尡 Day 7/90 – DSA Pattern Challenge | Fast & Slow Pointers 馃敟 Today I explored one of the most elegant and powerful DSA patterns — Fast & Slow Pointer (Hare & Tortoise) 馃殌 At first 馃敆 LeetCode 141 | Linked List Cycle – Fast & Slow Pointer Explained in C++In this video, we solve LeetCode Question 141: Linked List Cycle using the Fast & S Using Fast & Slow pointers to detect cycles without extra space. Connect with me: / pratyushnarain55555 / padho_with_pratyush The slow fast pointer dsa pattern is one of the most powerful patterns while dealing with linked list questions. This pattern involves maintaining two pointers that traverse a data structure (like an array or linked list) at different speeds. K rotations Pattern: Fast and slow pointers Understanding the fast and slow pointer pattern Identifying the fast and slow pointer pattern Middle node search Split list in half newEqual halves Jul 21, 2024 路 The fast pointer moves two steps for every one step the slow pointer moves. 11. Apr 12, 2025 路 馃摌 What is Fast and Slow Pointer? Two pointers are used: Slow Pointer (Tortoise) – moves 1 step at a time Fast Pointer (Hare) – moves 2 steps at a time When both pointers are used on a data structure (like a linked list), their interaction can help detect cycles, find the middle, check for palindromes, and more. The slow pointer moves one step, the fast pointer moves two steps. When the fast pointer completes i-1 full cycles, it travels (i-1) * n distance. Apr 9, 2024 路 The essence of the slow and fast pointer technique lies in utilizing two pointers — typically labeled “slow” and “fast” — that traverse a data structure at distinct speeds. slow = slow -> next and fast pointer by two nodes i. Nov 24, 2023 路 Fast and slow pointers are a common pattern used in algorithmic problem-solving, particularly in linked list and two-pointer problems. Here's the speed difference that makes it magical: L2. Two Pointers 2. If there’s a cycle, the fast pointer will eventually meet the slow pointer; if not, the fast pointer will reach the end of the list. Jan 30, 2021 路 That's when I discovered fast and slow pointers and it has now opened up a whole world of possibilities. Master this technique to solve half of linked list problems easily on platforms like In this video, we complete our three-part series on the two-pointer series where we leverage two different pointers at two different speeds. Fast and Slow Pointer The fast and slow pointer technique (also known as the tortoise and hare algorithm) uses two pointers to determine traits about directional data structures. To cover the remaining distance in the cycle, the fast pointer needs to travel an additional n - k to meet the slow pointer. 17K subscribers Subscribed Jul 23, 2025 路 After each iteration where the slow pointer moves one step forward and the fast pointer moves two steps forward, the distance between the two pointers increases. Dec 11, 2022 路 How to use fast and slow pointer technique to solve a pattern of problems of linked list. If the fast pointer ever catches up to the slow pointer, there is a loop in the linked list. Jan 10, 2026 路 馃敼 Two Pointer / Fast–Slow Pointer (Amazon Favorite) Amazon asks these a ton—expect cycle/palindrome twists in onsites. In this video, we walk through a difficult problem Aug 24, 2024 路 Remove Duplicates from Sorted Array Problem: Use two pointers to remove duplicates from a sorted array in place. If the Hare (fast pointer) is two steps behind the Tortoise (slow pointer): The fast pointer moves two steps and the slow pointer moves one step. Nov 24, 2023 路 If there’s a cycle, the fast pointer will eventually catch up to the slow pointer. Difficulty: Medium Remove Nth Node From End of List Problem: Remove the nth node from the end of a linked list using two pointers Jul 31, 2023 路 Else, move the slow pointer by one node i. If fast can move indefinitely, it means there is a cycle, and slow and fast will eventually meet. Full explanation in the main video 馃憞#Shorts #DSA #LeetCode #LinkedList #Coding #Progra Steps: Find the middle using fast & slow pointers Reverse the second half of the list Compare both halves node by node This approach avoids extra space and works in linear time. LeetCode 141 – Linked List Cycle Detection using Fast & Slow pointers. Being able to succinctly perform these tasks in a timely fashion and communicate your ideas in a coherent manner is what can make the difference in thousands of dollars of Jul 23, 2025 路 After each iteration where the slow pointer moves one step forward and the fast pointer moves two steps forward, the distance between the two pointers increases. This is useful for finding cycles in linked lists. The python code for this is very simple. 2 days ago 路 Fast and Slow Pointers is a powerful pattern where you use two pointers and move them at different speeds. next return fast is None These practice problems demonstrate different applications and variations of the fast and slow pointers technique. Learn coding with 30 Days Coding We've Launched a New Platform! 30dayscoding. next: fast = fast. fast = fast -> next -> next. md 2025-07-02 Complete LeetCode DSA Patterns Cheatsheet Table of Contents 1. If there is a cycle, the fast pointer will eventually lap the slow pointer, causing them to meet. Each time, fast moves two steps, and slow moves one step. Jul 11, 2025 路 The slow pointer, on the other hand, has traveled a distance m where m is exactly k plus one complete cycle if i is greater than 1. Fast and Slow Pointers || 25 DSA Patterns || New & Easy way to Master DSA || Crack FAANG OffTheCollege 8. e. If a cycle exists, the two pointers will eventually meet during traversal. com has evolved into SkillSetMaster Check out skillsetmaster. In Lecture 7, we'll dive into the magic of fast and slow pointers in software engineering and data structures. In this technique Sep 15, 2025 路 Ever wondered how to detect if a linked list has a cycle without using extra memory? The Fast & Slow Pointers technique, also known as Floyd’s Cycle Detection Algorithm, is your secret weapon Get Unlimited Access to Articles Placeholder text :) In technical interviews, you will be expected to code up an efficient algorithm, talk comfortably about the design, analysis and tradeoffs of a specific algorithm. If fast reaches the end, it means there is no cycle. Initially, if the slow pointer is at a distance k from a certain point in the cycle, then after one iteration, the distance between the slow and fast pointers becomes k+1. If the list has a cycle, they'll eventually meet inside the loop and we return true. The slow pointer moves one step at a time, while the fast pointer moves by two steps. dsa-patterns. In this chapter, we will focus on slow-pointer and fast-pointer problem in the linked list and show you how to solve this problem. If the slow pointer moved at 2 steps, however, the meeting would be guaranteed. This pr 4 days ago 路 It uses two pointers moving at different speeds: a "slow" pointer (tortoise) that advances 1 step at a time and a "fast" pointer (hare) that advances 2 steps at a time. Here is explained 6 problems related to it with solutions. This video breaks down LeetCode Problem 141 step by step using the Fast & Slow Pointer (Floyd’s Cycle Detection) technique; one of the most frequently asked DSA problems in MAANG and product 2 days ago 路 In this video, we solve LeetCode 202 – Happy Number using Java, with a clear explanation of Floyd’s Cycle Detection Algorithm (Fast and Slow Pointer). Nov 25, 2023 路 One elegant solution to this problem is Floyd's slow and fast pointers approach, often likened to two individuals running on a racetrack. Why direction consistency (all forward or all backward) is critical to validate a loop. fast = head while fast and fast. next. By solving these and similar problems, you’ll gain confidence in applying this powerful method to a wide range of linked list challenges. Here's the speed difference that makes it magical: Dec 11, 2022 路 How to use fast and slow pointer technique to solve a pattern of problems of linked list. Fast & Slow Learn how to change the settings of the mouse buttons, mouse wheel, and pointer. Please login to see more details. Jul 11, 2025 路 After each iteration where the slow pointer moves one step forward and the fast pointer moves two steps forward, the distance between the two pointers increases. Jan 13, 2026 路 View dsa-patterns. However, the second scenario, which is also called slow-pointer and fast-pointer technique, is really useful. . Difficulty: Easy Sort Colors Problem: Sort an array of colors using a two-pointer technique. Ace your coding interviews with this efficient O (n) solution! 馃尡Day 7/90 – DSA Pattern Challenge Today I stepped into one of the most powerful DSA patterns — Fast & Slow Pointer 馃敟 I learned how using two pointers at different speeds helps us solve 18 hours ago 路 Learn how to detect a cycle in a linked list using the Fast & Slow Pointer technique (Floyd’s Cycle Detection Algorithm) — one of the most important problems for coding interviews. K rotations Pattern: Fast and slow pointers Understanding the fast and slow pointer pattern Identifying the fast and slow pointer pattern Middle node search Split list in half newEqual halves Sep 2, 2025 路 The fast and slow pointer technique is a specialized variant of the two-pointer pattern, characterized by the differing speeds at which two pointers traverse a data structure. While the The Fast & Slow pointer approach, also known as the Hare & Tortoise algorithm, is a pointer algorithm that uses two pointers which move through the array (or Jul 23, 2025 路 Move the fast pointer two nodes at a time, while moving the slow pointer one node at a time. If the fast pointer moves 3 steps and slow pointer at 1 step, it is not guaranteed for both pointers to meet in cycles containing even number of nodes. Being able to succinctly perform these tasks in a timely fashion and communicate your ideas in a coherent manner is what can make the difference in thousands of dollars of Oct 31, 2022 路 In the Fast & Slow Pointers technique, two pointers start at the same position and iterate through an array (or linked list) at different speeds. From what I've very briefly read, the concept is that you traverse a linked list with two pointers, one moving one node per iteration and one at two nodes per iteration (slow and fast respectively). Due to the different speeds of the pointers, this pattern is also commonly known as the Hare and Tortoise algorithm, where the Hare is the fast pointer while Tortoise is the slow pointer. Master the 'Find Middle of Linked List' problem using the Slow and Fast Pointer (Tortoise and Hare) technique. Typically, the slow pointer moves one step at a time while the fast pointer moves two steps at a time. com for new courses and improved learning experience Oct 23, 2019 路 Here is the proof: If the Hare (fast pointer) is one step behind the Tortoise (slow pointer): The fast pointer moves two steps and the slow pointer moves one step, and they both meet. At this point, they meet. What Are Slow and Fast Pointers? Slow and fast pointers is a technique where two pointers traverse a data structure at different speeds. It can help you solve multiple linked lists and array related problems like: Given two pointers, named slow and fast, both start at the head of the list. The fast pointer has caught up to the slow pointer which means the list contains a cycle. This can be an array, singly-linked list, or a graph. Get Unlimited Access to Articles Placeholder text :) In technical interviews, you will be expected to code up an efficient algorithm, talk comfortably about the design, analysis and tradeoffs of a specific algorithm. Here is explained 6 problems related to it. Sliding Window 3. Fast and slow pointers are a powerful technique, and recognizing scenarios where this pattern can be applied can lead to efficient solutions for various algorithmic problems. At any point, if the fast and the slow pointers point to the same node, return True as a loop has been detected.