Fast And Slow Pointer Leetcode. Typically they starts from the left end, then the first pointer

Typically they starts from the left end, then the first pointer advances fast and give some feedback to the slow pointer and do some calculation. Here's the speed difference that makes it magical: 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 sequence/LinkedList) at different speeds. Solved: Middle of the Linked List (LeetCode 876) Today I solved a classic linked list problem that strengthens the Fast & Slow pointer pattern. I find myself stabilised in LeetCode Easy questio do comapnies hires final year btech cse students in jan-may?? However, the second scenario, which is also called slow-pointer and fast-pointer technique, is really useful. io/ In this video, I talk about Fast and Slow Pointers LeetCode Pattern. You must solve the problem without modifying the array nums and using only constant extra space. jpg] Input: head = [1,2,3,4,5] Output: [3,4,5] Explanation: The middle node of the list is node 3. Solution Idea: Define two pointers, Slow and FAST, let Fast take the K step, then two pointers together, then the difference between them has been K, then when Fast is Null, the end of the flag , SLOW at this time is the countdown knior needed. If fast reaches the end, it means there is no cycle. I [Java] Leetcode 19/203 Linked List Deletion [Fast & Slow Pointers #2] Eric Programming • 2K views • 4 years ago Help with Two Pointer techniques Hello, I have been working with the Two Pointer pattern for the past few days and am struggling with identifying when to use each type of two pointer (ie. Given two pointers, named slow and fast, both start at the head of the list. Example 1: Input: nums = [1,3,4,2,2] Output Example 1: [https://assets. This repo contains all the most important LeetCode questions organized topic-wise like Arrays, Strings, Trees, and DP. If fast can move indefinitely, it means there is a cycle, and slow and fast will eventually meet. Slow moves by 1 node at a time, Fast moved by 2 nodes at a time If there is a cycle, they will eventually coincide 2. While the fast one increases by two steps, the slow pointer will increase by just one step. Problem solved today LeetCode 141 – Linked List Cycle Detection using Fast & Slow pointers. 🔗 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 Day 27 Problem solving on leetcode 1Day = 1 Question on leetcode 👍 👍 🚀 LeetCode 876 | Middle of the Linked List This problem is a classic example of using the fast and slow pointer Key ideas: Use fast & slow pointers to find the midpoint Handle even and odd length cases correctly Ensure the first list has one extra node when the length is odd Carefully reconnect pointers to This Linked List Trick Gets Asked Everywhere 😱Fast & Slow Pointer Explained FAST | Leetcode 141 TechnoPathy Subscribe Subscribed 2 days ago · By the time the fast pointer reaches the end (or catches up to the slow pointer in a cycle), the slow pointer will be at a position of interest, like the middle of the list or the cycle entry point. 📁 Folder Structure study-plan/ ├── README. Aug 24, 2024 · Hey, LeetCode Community, I want a guidance from you all, I am just a basic coder, who is stuck in arrays. Full explanation in the main video Link in Comments 👇#Shorts #DSA #LeetCode #LinkedLis 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 sequence/ LinkedList) at 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. next Can you solve this real interview question? Linked List Cycle - Given head, the head of a linked list, determine if the linked list has a cycle in it. 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 sequence/LinkedList) at different speeds. This is the best place to expand your knowledge and get prepared for your next interview. The fast pointer moves through the list at twice the speed of the slow pointer. The fast jumps by two positions while the slow by one. nextandfast. ). This technique is often employed in cycle detection in linked lists. 06K subscribers Subscribed Mathematical Insight The fast pointer moves twice as fast as the slow pointer. md (this file) ├── 01-two-pointers/ │ ├── README. Each time, fast moves two steps, and slow moves one step. Typically, the slow pointer moves one step at a time while the fast pointer moves two steps at a time. Insight/Solution: Slow and fast pointers, the fast pointer starts one node after the slow node and moves one extra node further each time if slow == fast: there is a cycle Can you solve this real interview question? Find the Duplicate Number - Level up your coding skills and quickly land a job. Determine where the cycle is You now have a pointer A to the position where slow and fast meet Introduce a third pointer B that points to HEAD iterate moving A and B ahead by 1 until they meet. Note that We would like to show you a description here but the site won’t allow us. Oct 23, 2019 · In Coding Patterns series, we will try to recognize common patterns underlying behind each algorithm question, using real examples from Leetcode. com/uploads/2021/07/23/lc-midlist1. This means that for every increment of the slow pointer, the fast pointer moves two nodes ahead. It’s perfect for anyone preparing for coding interviews or looking to improve problem-solving skills. The goal is to find the middle node efficiently in a 📅 Day 10 / 90 – Babua DSA Patterns 2026 🚀 | Fast & Slow Pointers Today’s focus was a single but powerful problem that ties together multiple core ideas of linked lists and pointers: 🔗 Day 18 of a 100-day pattern-based DSA learning journey 📈 Today I solved a medium-level problem and wrapped up the Slow and Fast Pointer pattern after additional practice. In the last chapter, we have introduced how to use the two-pointer technique in a linked list. May 19, 2025 · In this blog, let us explore one of the most powerful and elegant strategies in linked list problems, the fast and slow pointer technique (my favourite one ). Established a set (2-3 Jan 13, 2022 · Next type is using two pointers with different speed of movement. In this playlist, you'll explore how to use a slow pointer and a fast pointer to detect cycles, find the middle of linked lists, detect palindromes, and solve many more problems efficiently. There is a cycle in a linked list if there is some node in the list that can be reached again by continuously following the next pointer. Problem Highlights 🔗 Leetcode Link: Middle of the Linked List 💡 Difficulty: Easy ⏰ Time to complete: 10 mins 🛠️ Topics: Linked List, Two Pointer 🗒️ Similar Questions: Delete the Middle Node of a Linked List, Maximum Twin Sum of a Linked List 1: U-nderstand Understand what the interviewer is asking for by using test cases and questions about the problem. If they intersect, there is a cycle, otherwise no. If a cycle exists, the fast pointer will eventually catch up to the slow pointer. This approach is quite useful when dealing with cyclic LinkedLists or arrays. 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. [Java] Leetcode 19/203 Linked List Deletion [Fast & Slow Pointers #2] Eric Programming • 2K views • 4 years ago May 31, 2025 · The Fast and Slow Pointer technique involves two pointers that move through a data structure (usually a linked list or array) at different speeds — one moves twice as fast as the other. If there is no cycle, return null. Each question has a clean and optimized solution with detailed explanations. Oct 20, 2018 · The fast pointer actually become useless after finding the middle point After we find the middle node (after fast reach to the end), we split the linked list to left sublist (that’s why I used a prevSlow pointer, since we need to cut the list off at the middle pointer in order to use the left sublist!) and right sublist, which would also be Jan 30, 2021 · That's when I discovered fast and slow pointers and it has now opened up a whole world of possibilities. So my question is, are all fast and slow pointer questions solvable using hash maps? Aug 21, 2022 · hey you! it's me :)today we're combining two of our previous topics: linked lists and two pointers. Grind 75 Problems The Fast & Slow Pointers technique is essential for solving the following Grind 75 problems: Linked List Cycle (LeetCode #141) Find Duplicate Number (LeetCode #287) Aug 3, 2022 · Slow and fast pointer, one pointer moving slow (1 step for instance) and another moving fast (2 steps or variable number of steps). Example 1: Input: nums = [1,3,4,2,2] Output After watching this video, you'll understand slow and fast pointers thoroughly. Delete the middle node, and return the . Nov 24, 2023 · If there’s a cycle, the fast pointer will eventually catch up to the slow pointer. Can you solve this real interview question? Delete the Middle Node of a Linked List - You are given the head of a linked list. I find myself stabilised in LeetCode Easy questio do comapnies hires final year btech cse students in jan-may?? Apr 6, 2024 · We can keep two pointers while traversing a linked list: fast and slow. Internally, pos is used to denote the index of the node that tail's next pointer is connected to. md ├── 02-sliding-window/ │ ├── README. 🔁 Fast & Slow Pointer Pattern — Revisited Spent some time revisiting the Fast–Slow Pointer (Floyd’s Cycle Detection) pattern today — one of those techniques that quietly shows up in Explanation: Use two different pointers, one is going to be a slow pointer and another one will be a fast pointer that moves twice the number of nodes of the slow pointer in a single iteration. Level up your coding skills and quickly land a job. md ├── 03-fast-slow-pointers/ │ ├── README. 4 days ago · The fast pointer is ahead of the slow by n nodes, and they both keep moving one step at a time. May 19, 2025 · What is Fast and slow pointer technique ? This approach uses two pointers at different speeds through a data structure (mainly linked list ) to detect patterns such as cycles or finding midpoints. Apr 6, 2024 · LeetCode Meditations — Interlude: Fast & Slow Pointers Before we start the next problem in the series, let's take a quick look at a technique that comes in handy when it comes to working with linked lists. This can be an array, singly-linked list, or a graph. md (and so on for each pattern) Enter a linked list to output the kth knot in the linked list. Dec 9, 2025 · Learn all variants, when to use each pattern, complete templates in multiple languages, and a systematic approach to solve any two pointers problem. fast/slow, front/back, etc. It turned out to be some work since the pointer updating is not all that trivial. 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 sequence/ LinkedList) at different speeds. In this video I show how Example 1: [https://assets. There is only one repeated number in nums, return this repeated number. Example 1: Input: nums = [1,3,4,2,2] Output A curated list of leetcode questions grouped by their common patterns Oct 20, 2018 · The fast pointer actually become useless after finding the middle point After we find the middle node (after fast reach to the end), we split the linked list to left sublist (that’s why I used a prevSlow pointer, since we need to cut the list off at the middle pointer in order to use the left sublist!) and right sublist, which would also be Jan 12, 2024 · 在链表操作中，快慢指针 (Fast & Slow Pointers) 是一种极其经典且优雅的技巧。它主要用于解决链表中的环路检测、中点寻找等问题。其背后的理论基础通常被称为 Floyd 判圈算法 (Floyd’s Cycle-Finding Algorithm)，有时也形象地被称为「龟兔赛跑算法」。 Jan 13, 2022 · Next type is using two pointers with different speed of movement. ” It teaches you reusable patterns like sliding window, two pointers, merge intervals, and fast/slow pointers — the same patterns used to solve 70% of LeetCode problems. Starting from 2 different arrays, for merging etc. Apr 9, 2023 · "Unlock the secrets of the Fast & Slow Pointer technique in this ultimate coding tutorial! 💡 Ace your next FAANG interview with these 3 essential examples, Jan 26, 2025 · Two Pointers in 7 minutes | LeetCode Pattern AlgoMasterIO 9. Can you solve this real interview question? Find the Duplicate Number - Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive. nextfast=fast. Example 1: Input: nums = [1,3,4,2,2] Output Floyd's Algorithm Keep a fast and a slow pointer. By the time the fast gets to the end, the slow would be just right before the node that we need to remove. Example 1: Input: nums = [1,3,4,2,2] Output Jun 19, 2024 · Fast and Slow Pointers The Fast and Slow Pointers technique, also known as the Tortoise Tagged with datastructures, algorithms, coding, interview. The thing I'm noticing is, every question I'm given to use the fast and slow pointers technique on, I've found a solution using hash maps instead. Have both slow and slow2 advance by one. Note that What Are Slow and Fast Pointers? Slow and fast pointers is a technique where two pointers traverse a data structure at different speeds. Window length is five, replacements needed is two, exactly equal to K, so it's valid. To find where the cycle starts, make another slow pointer. 9 Approaches: Count, Hash, In-place Marked, Sort, Binary Search, Bit Mask, Fast Slow Pointers Pinned longluo Mar 29, 2022 Hash Table Two Pointers Binary Search Bit Manipulation 1+ 605 66K 37 C++ || Algorithm || 4 Approaches || Binary Search || Brute Force || cnt array || map Pinned KnockCat Mar 29, 2022 C Binary Tree 369 64K 30 Java Linked This repository is a structured LeetCode roadmap designed to help you master Data Structures and Algorithms (DSA) using Python. The rest shall be straightforward. next. Jan 4, 2025 · The Fast and Slow Pointer technique is a powerful and versatile approach to solve problems involving cycles in linked lists or arrays… I use slow and fast two pointers to traverse at the same time, slow moves 1 step each iteration, while fast 2. In this technique Can you solve this real interview question? Linked List Cycle II - Given the head of a linked list, return the node where the cycle begins. Oct 1, 2024 · Fast and Slow Pointers: In this approach, one pointer moves faster than the other. Jun 19, 2024 · Fast and Slow Pointers The Fast and Slow Pointers technique, also known as the Tortoise and Hare algorithm, is a powerful method used to solve problems related to cycle detection in linked lists and arrays, as well as finding the middle of a linked list and other similar tasks. Sep 2, 2025 · 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. At each iteration, I first delete out fast from its original position, then insert it in front of slow. Where they intersect is the head of the cycle # Determine if the linked list contains a leetcode 中文 | Happy Number | Fast and Slow pointers 基礎概念 3 - Python - LeetCode 202 今天比昨天厲害 • 511 views • 4 years ago Help with Two Pointer techniques Hello, I have been working with the Two Pointer pattern for the past few days and am struggling with identifying when to use each type of two pointer (ie. 3 days ago · While many algorithm books focus on the “what,” this one focuses on the “how. leetcode, coding interview question, data structures, data structures and algorithms, linked lists, fast and slow pointers Leetcode coding problem 142 (Medium): Given a linked list, return the node where the cycle begins. md │ └── questions. Feb 9, 2024 · Approach The solution utilizes two pointers, fast and slow, both starting at the head of the list. I found some lists such as These Tips from Sean Prashad however I still find myself having to guess most of the time. 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. Can you solve this real interview question? Linked List Cycle - Given head, the head of a linked list, determine if the linked list has a cycle in it. md (and so on for each pattern) Oct 23, 2019 · In Coding Patterns series, we will try to recognize common patterns underlying behind each algorithm question, using real examples from Leetcode. I'm running through the different patterns for leetcode questions, and I'm currently on fast and slow pointers. we will use two pointers, to find the middle of a linked Feb 12, 2024 · Fast and Slow Pointer Similar to the two pointers pattern, the fast and slow pointers pattern uses two pointers to traverse an iterable data structure at different speeds. We'll cover examples for even and odd-length linked lists to help you write e Unlock the power of the Fast and Slow Pointers Pattern — one of the most important and frequently asked techniques in coding interviews for FAANG, product-based companies, and top startups. Fast and Slow Pointers パターンの基本アイデア Fast and Slow Pointers パターン （別名 Floyd’s Tortoise and Hare アルゴリズム）は、主に 単方向につながったデータ構造 （例: リンクリスト、配列など）を扱う際に利用される手法です。 Example 1: [https://assets. May 31, 2025 · The Fast and Slow Pointer technique involves two pointers that move through a data structure (usually a linked list or array) at different speeds — one moves twice as fast as the other. Level up your coding skills and quickly land a job. Suggest me the best resources and topics to study, so that I can do better in CP and LeetCode. We would like to show you a description here but the site won’t allow us. Internally, pos is used to denote the index of the node that tail's next pointer is You start with slow and fast pointer. Nov 22, 2019 · 基本上呢，做法就是指定兩個 pointer - fast 跟 slow，一開始 slow 跟 fast 都指向 head，接下來，在 fast 走到 linked list 的底端前，fast 一次走兩步，slow 一次走一步，當 fast 走到底的時候，slow 就會在中間。 Can you solve this real interview question? Find the Duplicate Number - Given an array of integers nums containing n + 1 integers where each integer is in the range [1, n] inclusive. Count of B becomes two, max count is still three. Using this pattern, you can solve multiple arrays and linked lists problems Midpoint of linked list - use two pointers and have fast pointer move twice as fast as slow, so when it's at the end of the list, slow is at the midpoint whilefast. The fast and slow pointers pattern—also known as the "tortoise and hare" algorithm—is one of the most elegant solutions in computer science. Master DSA Patterns: https://algomaster. leetcode. Now the right pointer reads B. Feb 28, 2025 · Fast and Slow Pointers パターン 1. next: slow=slow. It follows a topic-wise progression, covering Easy, Medium, and Hard problems with optimized solutions and explanations. Example 1: [https://assets.

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