{"id":6952,"date":"2025-06-18T14:20:43","date_gmt":"2025-06-18T08:50:43","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=6952"},"modified":"2025-06-18T14:20:44","modified_gmt":"2025-06-18T08:50:44","slug":"add-two-numbers-represented-by-linked-lists","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/add-two-numbers-represented-by-linked-lists\/","title":{"rendered":"Add Two Numbers Represented by Linked Lists"},"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>You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each node contains a single digit. Add the two numbers and return the result as a linked list.<\/p>\n  <p>You may assume the two numbers do not contain any leading zeros, except the number 0 itself.<\/p>\n\n  <h2>Examples:<\/h2>\n  <p><strong>Input:<\/strong> l1 = [2,4,3], l2 = [5,6,4]<br><strong>Output:<\/strong> [7,0,8]<br><strong>Explanation:<\/strong> 342 + 465 = 807<\/p>\n\n  <p><strong>Input:<\/strong> l1 = [0], l2 = [0]<br><strong>Output:<\/strong> [0]<\/p>\n\n  <p><strong>Input:<\/strong> l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]<br><strong>Output:<\/strong> [8,9,9,9,0,0,0,1]<\/p>\n\n  <h2>Constraints:<\/h2>\n  <ul>\n    <li>The number of nodes in each linked list is in the range [1, 100].<\/li>\n    <li>0 &le; Node.val &le; 9<\/li>\n    <li>It is guaranteed that the list represents a number that does not have leading zeros.<\/li>\n  <\/ul>\n\n  <h2>Approach:<\/h2>\n  <ul>\n    <li>Initialize a dummy node to build the result list and a <code>carry<\/code> variable set to 0.<\/li>\n    <li>Traverse both linked lists simultaneously. For each node, compute the sum of values plus carry.<\/li>\n    <li>Create a new node with <code>sum % 10<\/code> and update carry to <code>sum \/ 10<\/code>.<\/li>\n    <li>Continue until both lists are exhausted and carry becomes 0.<\/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 length of the longer list.<\/li>\n    <li><strong>Space Complexity:<\/strong> O(n) for the new list created.<\/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 addTwoNumbers = function(l1, l2) {\n    let dummy = new ListNode(0);\n    let curr = dummy;\n    let carry = 0;\n\n    while (l1 || l2 || carry) {\n        let sum = (l1?.val || 0) + (l2?.val || 0) + carry;\n        carry = Math.floor(sum \/ 10);\n        curr.next = new ListNode(sum % 10);\n        curr = curr.next;\n        l1 = l1?.next;\n        l2 = l2?.next;\n    }\n\n    return dummy.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* addTwoNumbers(struct ListNode* l1, struct ListNode* l2) {\n    struct ListNode dummy = {0, NULL};\n    struct ListNode* curr = &dummy;\n    int carry = 0;\n\n    while (l1 || l2 || carry) {\n        int sum = carry + (l1 ? l1->val : 0) + (l2 ? l2->val : 0);\n        carry = sum \/ 10;\n        curr->next = malloc(sizeof(struct ListNode));\n        curr = curr->next;\n        curr->val = sum % 10;\n        curr->next = NULL;\n        if (l1) l1 = l1->next;\n        if (l2) l2 = l2->next;\n    }\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* addTwoNumbers(ListNode* l1, ListNode* l2) {\n        ListNode* dummy = new ListNode();\n        ListNode* curr = dummy;\n        int carry = 0;\n\n        while (l1 || l2 || carry) {\n            int sum = carry;\n            if (l1) { sum += l1->val; l1 = l1->next; }\n            if (l2) { sum += l2->val; l2 = l2->next; }\n            carry = sum \/ 10;\n            curr->next = new ListNode(sum % 10);\n            curr = curr->next;\n        }\n\n        return dummy->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 addTwoNumbers(ListNode l1, ListNode l2) {\n        ListNode dummy = new ListNode(0);\n        ListNode curr = dummy;\n        int carry = 0;\n\n        while (l1 != null || l2 != null || carry != 0) {\n            int sum = carry;\n            if (l1 != null) { sum += l1.val; l1 = l1.next; }\n            if (l2 != null) { sum += l2.val; l2 = l2.next; }\n            carry = sum \/ 10;\n            curr.next = new ListNode(sum % 10);\n            curr = curr.next;\n        }\n\n        return dummy.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\">\nclass Solution(object):\n    def addTwoNumbers(self, l1, l2):\n        dummy = ListNode(0)\n        curr = dummy\n        carry = 0\n\n        while l1 or l2 or carry:\n            sum = carry\n            if l1:\n                sum += l1.val\n                l1 = l1.next\n            if l2:\n                sum += l2.val\n                l2 = l2.next\n            carry = sum \/\/ 10\n            curr.next = ListNode(sum % 10)\n            curr = curr.next\n\n        return dummy.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 AddTwoNumbers(ListNode l1, ListNode l2) {\n        ListNode dummy = new ListNode(0);\n        ListNode curr = dummy;\n        int carry = 0;\n\n        while (l1 != null || l2 != null || carry != 0) {\n            int sum = carry;\n            if (l1 != null) { sum += l1.val; l1 = l1.next; }\n            if (l2 != null) { sum += l2.val; l2 = l2.next; }\n            carry = sum \/ 10;\n            curr.next = new ListNode(sum % 10);\n            curr = curr.next;\n        }\n\n        return dummy.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: You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order, and each node contains a single digit. Add the two numbers and return the result as a linked list. You may assume the two numbers do not contain any leading zeros, except the number 0<\/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-6952","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\/6952","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=6952"}],"version-history":[{"count":1,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6952\/revisions"}],"predecessor-version":[{"id":6953,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/6952\/revisions\/6953"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=6952"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=6952"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=6952"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}