{"id":6903,"date":"2025-06-17T20:40:51","date_gmt":"2025-06-17T15:10:51","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=6903"},"modified":"2025-06-17T20:40:52","modified_gmt":"2025-06-17T15:10:52","slug":"remove-nth-node-from-end-of-singly-linked-list-one-pass-approach","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/remove-nth-node-from-end-of-singly-linked-list-one-pass-approach\/","title":{"rendered":"Remove Nth Node From End of Singly Linked List (One Pass Approach)"},"content":{"rendered":"\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_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  .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>Given the head of a linked list, remove the <code>n<\/code>th node from the end of the list and return its head.<\/p>\n  \n    <h2>Approach (Optimized Two-Pointer):<\/h2>\n    <ul>\n      <li>Use a dummy node before the head to handle edge cases easily.<\/li>\n      <li>Move the first pointer <code>n<\/code> steps ahead.<\/li>\n      <li>Move both first and second pointers until first reaches the end.<\/li>\n      <li>Now second is just before the node to be deleted. Skip it using <code>second.next = second.next.next<\/code>.<\/li>\n    <\/ul>\n  \n    <h2>Time and Space Complexity:<\/h2>\n    <ul>\n      <li><strong>Time Complexity:<\/strong> O(n)<\/li>\n      <li><strong>Space Complexity:<\/strong> O(1)<\/li>\n    <\/ul>\n  <\/div>\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=\"c\">C<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"cpp\">C++<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"java\">Java<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"py\">Python<\/button>\n    <button class=\"wp_blog_code-tab-button\" data-lang=\"csharp\">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 removeNthFromEnd = function(head, n) {\n    let sentinel = new ListNode(0, head);\n    let first = sentinel;\n\n    for (let i = 0; i < n; i++) {\n        first = first.next;\n    }\n\n    let second = sentinel;\n    while (first.next) {\n        first = first.next;\n        second = second.next;\n    }\n\n    second.next = second.next.next;\n    return sentinel.next;\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* removeNthFromEnd(struct ListNode* head, int n) {\n    struct ListNode dummy = {0, head};\n    struct ListNode *first = &dummy, *second = &dummy;\n\n    for (int i = 0; i < n; i++) {\n        first = first->next;\n    }\n\n    while (first->next) {\n        first = first->next;\n        second = second->next;\n    }\n\n    struct ListNode* temp = second->next;\n    second->next = second->next->next;\n    free(temp);\n\n    return dummy.next;\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* removeNthFromEnd(ListNode* head, int n) {\n        ListNode* sentinel = new ListNode(0, head);\n        ListNode* first = sentinel;\n        ListNode* second = sentinel;\n\n        for (int i = 0; i < n; ++i) first = first->next;\n\n        while (first->next) {\n            first = first->next;\n            second = second->next;\n        }\n\n        ListNode* toDelete = second->next;\n        second->next = second->next->next;\n        delete toDelete;\n\n        return sentinel->next;\n    }\n};\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 removeNthFromEnd(ListNode head, int n) {\n        ListNode sentinel = new ListNode(0);\n        sentinel.next = head;\n        ListNode first = sentinel;\n        ListNode second = sentinel;\n\n        for (int i = 0; i < n; i++) {\n            first = first.next;\n        }\n\n        while (first.next != null) {\n            first = first.next;\n            second = second.next;\n        }\n\n        second.next = second.next.next;\n        return sentinel.next;\n    }\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\">\n# Definition for singly-linked list.\nclass ListNode(object):\n    def __init__(self, val=0, next=None):\n        self.val = val\n        self.next = next\n\nclass Solution(object):\n    def removeNthFromEnd(self, head, n):\n        \"\"\"\n        :type head: Optional[ListNode]\n        :type n: int\n        :rtype: Optional[ListNode]\n        \"\"\"\n        sentinel = ListNode(0, head)\n        first = sentinel\n\n        # Move first pointer n steps ahead\n        for _ in range(n):\n            first = first.next\n\n        second = sentinel\n        # Move both until first reaches the end\n        while first.next:\n            first = first.next\n            second = second.next\n\n        # Delete the nth node from end\n        second.next = second.next.next\n\n        return sentinel.next\n    <\/code><\/pre>\n  <\/div>\n\n  <!-- C# -->\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"csharp\">\n    <pre><code class=\"language-csharp\">\npublic class Solution {\n    public ListNode RemoveNthFromEnd(ListNode head, int n) {\n        ListNode sentinel = new ListNode(0, head);\n        ListNode first = sentinel;\n\n        for (int i = 0; i < n; i++) {\n            first = first.next;\n        }\n\n        ListNode second = sentinel;\n        while (first.next != null) {\n            first = first.next;\n            second = second.next;\n        }\n\n        second.next = second.next.next;\n        return sentinel.next;\n    }\n}\n    <\/code><\/pre>\n  <\/div>\n<\/div>\n\n<script>\n  document.addEventListener('DOMContentLoaded', () => {\n    const buttons = document.querySelectorAll('.wp_blog_code-tab-button');\n    const contents = document.querySelectorAll('.wp_blog_code-tab-content');\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","protected":false},"excerpt":{"rendered":"<p>Problem Statement: Given the head of a linked list, remove the nth node from the end of the list and return its head. Approach (Optimized Two-Pointer): Use a dummy node before the head to handle edge cases easily. Move the first pointer n steps ahead. Move both first and second pointers until first reaches the<\/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-6903","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\/6903","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=6903"}],"version-history":[{"count":1,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6903\/revisions"}],"predecessor-version":[{"id":6905,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6903\/revisions\/6905"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=6903"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=6903"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=6903"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}