{"id":6882,"date":"2025-06-17T18:50:15","date_gmt":"2025-06-17T13:20:15","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=6882"},"modified":"2025-06-17T18:50:16","modified_gmt":"2025-06-17T13:20:16","slug":"reverse-linked-list","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/reverse-linked-list\/","title":{"rendered":"Reverse Linked List"},"content":{"rendered":"\n\n<!-- PrismJS for Syntax Highlighting -->\n<link href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.min.css\" rel=\"stylesheet\">\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/prism.min.js\"><\/script>\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/plugins\/autoloader\/prism-autoloader.min.js\"><\/script>\n\n<style>\n.wp_blog_main-heading {\n  text-align: center;\n  font-size: 2.4rem;\n  color: #E58C32;\n  margin-top: 2.5rem;\n  font-weight: bold;\n}\n\n.wp_blog_explanation,\n.wp_blog_code-tabs-container {\n  max-width: 940px;\n  margin: 2rem auto;\n  padding: 2rem;\n  border-radius: 12px;\n  background-color: #f9fafb;\n}\n\n.wp_blog_explanation h2 {\n  font-size: 1.4rem;\n  color: #E58C32;\n  margin-bottom: 0.75rem;\n}\n\n.wp_blog_explanation p,\n.wp_blog_explanation li {\n  font-size: 1.05rem;\n  line-height: 1.7;\n  margin: 0.5rem 0;\n  color: #1f2937;\n}\n\n.wp_blog_explanation code {\n  padding: 3px 6px;\n  border-radius: 4px;\n  background: #e5e7eb;\n  font-family: 'Courier New', monospace;\n}\n\n.wp_blog_explanation img {\n  width: 100%;\n  border-radius: 12px;\n  margin-top: 1rem;\n}\n\n\/* Tabs *\/\n.wp_blog_code-tabs-header {\n  display: flex;\n  flex-wrap: wrap;\n  gap: 0.5rem;\n  margin-bottom: 1rem;\n}\n\n.wp_blog_code-tab-button {\n  padding: 0.6rem 1.2rem;\n  border: 1px solid #E58C32;\n  color: #E58C32;\n  border-radius: 50px;\n  font-weight: 600;\n  cursor: pointer;\n  background-color: white;\n  transition: background 0.3s ease, color 0.3s ease;\n}\n\n.wp_blog_code-tab-button.active {\n  background: #E58C32;\n  color: white;\n}\n\n\/* Code Panel *\/\n.wp_blog_code-tab-content {\n  display: none;\n  background: #111827;\n  border-radius: 12px;\n}\n\n.wp_blog_code-tab-content.active {\n  display: block;\n}\n\n.wp_blog_code-tab-content pre {\n  margin: 0;\n  padding: 1.5rem;\n  font-size: 1rem;\n  overflow-x: auto;\n  color: #f3f4f6;\n  background: #111827;\n  border-radius: 12px;\n}\n<\/style>\n\n<div class=\"wp_blog_explanation\">\n    <h2>Problem Statement:<\/h2>\n    <p>\n      Given the head of a singly linked list, reverse the list, and return the reversed list.\n    <\/p>\n  \n    <h2>Examples:<\/h2>\n    <ul>\n      <li><strong>Input:<\/strong> head = [1,2,3,4,5]<br>\n          <strong>Output:<\/strong> [5,4,3,2,1]<\/li>\n      <li><strong>Input:<\/strong> head = [1,2]<br>\n          <strong>Output:<\/strong> [2,1]<\/li>\n      <li><strong>Input:<\/strong> head = []<br>\n          <strong>Output:<\/strong> []<\/li>\n    <\/ul>\n  \n    <h2>Constraints:<\/h2>\n    <ul>\n      <li>The number of nodes in the list is in the range [0, 5000].<\/li>\n      <li>-5000 &le; Node.val &le; 5000<\/li>\n    <\/ul>\n\n    <h2>Approach:<\/h2>\n    <ul>\n    <li>Use three pointers: <code>prev<\/code>, <code>curr<\/code>, and <code>temp<\/code>.<\/li>\n    <li>In each step:\n      <ul>\n        <li>Save the next node.<\/li>\n        <li>Point current node\u2019s <code>next<\/code> to previous.<\/li>\n        <li>Move <code>prev<\/code> and <code>curr<\/code> forward.<\/li>\n      <\/ul>\n    <\/li>\n    <li>Return <code>prev<\/code> as the new head.<\/li>\n  <\/ul>\n  \n    <h2>Time and Space Complexity:<\/h2>\n    <ul>\n      <li><strong>Time Complexity:<\/strong> O(n), where n is the number of nodes in the list. We visit each node once.<\/li>\n      <li><strong>Space Complexity:<\/strong> O(1), since we reverse the list in-place using a constant number of pointers.<\/li>\n    <\/ul>\n<\/div>\n  \n\n<div class=\"wp_blog_code-tabs-container\">\n  <div class=\"wp_blog_code-tabs-header\">\n    <button class=\"wp_blog_code-tab-button active\" data-lang=\"js\">JavaScript<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"py\">Python<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"java\">Java<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"cpp\">C++<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"c\">C<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"cs\">C#<\/button>\n  <\/div>\n\n  <!-- JavaScript -->\n  <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n    <pre><code class=\"language-javascript\">\nvar reverseList = function(head) {\n    let prev = null;\n    let curr = head;\n    while (curr) {\n        let temp = curr.next;\n        curr.next = prev;\n        prev = curr;\n        curr = temp;\n    }\n    return prev;\n};\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- Python -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n    <pre><code class=\"language-python\">\nclass Solution:\n    def reverseList(self, head):\n        prev = None\n        curr = head\n        while curr:\n            temp = curr.next\n            curr.next = prev\n            prev = curr\n            curr = temp\n        return prev\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- Java -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n    <pre><code class=\"language-java\">\nclass Solution {\n    public ListNode reverseList(ListNode head) {\n        ListNode prev = null;\n        ListNode curr = head;\n        while (curr != null) {\n            ListNode temp = curr.next;\n            curr.next = prev;\n            prev = curr;\n            curr = temp;\n        }\n        return prev;\n    }\n}\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- C++ -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"cpp\">\n    <pre><code class=\"language-cpp\">\nclass Solution {\npublic:\n    ListNode* reverseList(ListNode* head) {\n        ListNode* prev = nullptr;\n        ListNode* curr = head;\n        while (curr != nullptr) {\n            ListNode* temp = curr->next;\n            curr->next = prev;\n            prev = curr;\n            curr = temp;\n        }\n        return prev;\n    }\n};\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- C -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n    <pre><code class=\"language-c\">\nstruct ListNode* reverseList(struct ListNode* head) {\n    struct ListNode* prev = NULL;\n    struct ListNode* curr = head;\n    while (curr) {\n        struct ListNode* temp = curr->next;\n        curr->next = prev;\n        prev = curr;\n        curr = temp;\n    }\n    return prev;\n}\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- C# -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n    <pre><code class=\"language-csharp\">\npublic class Solution {\n    public ListNode ReverseList(ListNode head) {\n        ListNode prev = null;\n        ListNode curr = head;\n        while (curr != null) {\n            ListNode temp = curr.next;\n            curr.next = prev;\n            prev = curr;\n            curr = temp;\n        }\n        return prev;\n    }\n}\n    <\/code><\/pre>\n  <\/div>\n<\/div>\n\n<script>\ndocument.addEventListener('DOMContentLoaded', () => {\n  const buttons = document.querySelectorAll('.wp_blog_code-tab-button');\n  const contents = document.querySelectorAll('.wp_blog_code-tab-content');\n\n  buttons.forEach(button => {\n    button.addEventListener('click', () => {\n      const lang = button.getAttribute('data-lang');\n      buttons.forEach(btn => btn.classList.remove('active'));\n      contents.forEach(content => content.classList.remove('active'));\n      button.classList.add('active');\n      document.querySelector(`.wp_blog_code-tab-content[data-lang=\"${lang}\"]`).classList.add('active');\n    });\n  });\n});\n<\/script>\n\n\n\n\n<p><\/p>\n","protected":false},"excerpt":{"rendered":"<p>Problem Statement: Given the head of a singly linked list, reverse the list, and return the reversed list. Examples: Input: head = [1,2,3,4,5] Output: [5,4,3,2,1] Input: head = [1,2] Output: [2,1] Input: head = [] Output: [] Constraints: The number of nodes in the list is in the range [0, 5000]. -5000 &le; Node.val &le;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"om_disable_all_campaigns":false,"_monsterinsights_skip_tracking":false,"_monsterinsights_sitenote_active":false,"_monsterinsights_sitenote_note":"","_monsterinsights_sitenote_category":0,"footnotes":""},"categories":[260,176,811,810,174,172,173],"tags":[],"class_list":{"0":"post-6882","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-c-c-plus-plus","7":"category-csharp","8":"category-data-structures-and-algorithms","9":"category-dsa","10":"category-java","11":"category-javascript","12":"category-python"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6882","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/comments?post=6882"}],"version-history":[{"count":1,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6882\/revisions"}],"predecessor-version":[{"id":6883,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6882\/revisions\/6883"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=6882"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=6882"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=6882"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}