{"id":9721,"date":"2025-08-28T17:10:18","date_gmt":"2025-08-28T11:40:18","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=9721"},"modified":"2025-09-30T12:30:53","modified_gmt":"2025-09-30T07:00:53","slug":"sum-of-first-n-numbers","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/sum-of-first-n-numbers\/","title":{"rendered":"Sum of first n numbers"},"content":{"rendered":"\n<!-- PrismJS for Syntax Highlighting -->\n<link\n    href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.min.css\"\n    rel=\"stylesheet\"\n\/>\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_theme {\n  --primary: #E58C32;\n  --secondary: #030302;\n  --light-bg: #fef9f4;\n  --text-dark: #2d2d2d;\n  --tab-radius: 12px;\n  --shadow: 0 4px 12px rgba(0, 0, 0, 0.08);\n  --code-bg: #001f3f;\n  --code-text: #d4f1ff;\n}\n\n.wp_blog_container {\n  font-family: 'Segoe UI', sans-serif;\n  background: var(--light-bg);\n  margin: 0;\n  padding: 0;\n  color: var(--text-dark);\n}\n\n\/* Heading *\/\n.wp_blog_main-heading {\n  text-align: center;\n  font-size: 2.4rem;\n  color: var(--primary);\n  margin-top: 2.5rem;\n  font-weight: bold;\n}\n\n\/* Explanation Card *\/\n.wp_blog_explanation,\n.wp_blog_code-tabs-container {\n  max-width: 940px;\n  margin: 2rem auto;\n  padding: 2rem;\n  background: white;\n  border-radius: var(--tab-radius);\n  box-shadow: var(--shadow);\n}\n\n\/* Text and Visuals *\/\n.wp_blog_explanation h2 {\n  font-size: 1.4rem;\n  color: var(--primary);\n  margin-bottom: 0.5rem;\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}\n\n.wp_blog_explanation code {\n  background: #fef9f4; 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\/* makes it the reference for absolute children *\/\n}\n\n.wp_blog_toggle-btn {\n  position: absolute;\n  top: 1rem;\n  right: 1rem;\n  z-index: 9999;\n  padding: 0.5rem 0.8rem;\n  border-radius: 10%;\n  background: var(--primary);\n  color: white;\n  font-weight: bold;\n  cursor: pointer;\n  border: none;\n  box-shadow: var(--shadow);\n  transition: background 0.3s, transform 0.2s;\n}\n\n.wp_blog_toggle-btn:hover {\n  background: #cc772e;\n}\n\n.wp_blog_theme.dark-mode .wp_blog_code-tabs-container {\n  background: #1e1e1e;\n}\n<\/style>\n\n<div class=\"wp_blog_container wp_blog_theme\">\n        <button id=\"blogNotesThemeToggle\" class=\"wp_blog_toggle-btn\">\ud83c\udf19<\/button>\n<h1 class=\"wp_blog_main-heading\"><\/h1>\n\n<div class=\"wp_blog_explanation\">\n    <h2>Problem Statement:<\/h2>\n    <p>\n       Write a function sum(n) that calculates the sum of the first n natural numbers using recursion. \n    <\/p>\n    <h2>Example:<\/h2>\n    <p><strong>Input:<\/strong> <code><strong>5<\/strong><\/code><\/p>\n    <p><strong>Process:<\/strong> 5 + 4 + 3 + 2 + 1 = 15<\/p>\n    <p><strong>Output:<\/strong> <code><strong>15<\/strong><\/code><\/p>\n\n\n    <h2>Concepts:<\/h2>\n    <ul>\n        <li><strong>Recursion:<\/strong> A technique where a <code>function calls<\/code> itself with a <code>reduced subproblem<\/code>.<\/li>\n        <li><strong>Base Case:<\/strong> <code>Stops recursion<\/code> to prevent <strong>infinite calls<\/strong>. Here, if <code>n === 0, return 0<\/code>.<\/li>\n        <li><strong>Recursive Case:<\/strong> <code>Return n + sum(n - 1).<\/code><\/li>\n    <\/ul>\n\n\n    <h2>Approach:<\/h2>\n    <ul>\n        <li>Use <code>recursion<\/code> to <strong>reduce<\/strong> the problem.<\/li>\n        <li><strong>Base case:<\/strong> if <code>n === 0<\/code>, <code>return 0<\/code>.<\/li>\n        <li><strong>Recursive case:<\/strong>return <code>n + sum(n-1)<\/code>.<\/li>\n        <li>This keeps adding numbers until <code>n<\/code> reaches <code>0<\/code>, giving the total <code>sum<\/code>.<\/li>\n    <\/ul>\n\n    <h2>Time &#038; Space Complexity:<\/h2>\n    <p><strong>Time Complexity: O(n)<\/strong> <code>one call<\/code> per value from <strong>n to 0<\/strong>.<\/p>\n    <p><strong>Space Complexity: O(n)<\/strong> due to <code>call stack<\/code> in <strong>recursion<\/strong>.<\/p>\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\">\n            JavaScript\n        <\/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    <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n        <pre><code class=\"language-javascript\">\nfunction sum(n) {\n  if (n === 0) return 0;\n  return n + sum(n - 1);\n}\nconsole.log(sum(5)); \/\/ 15\n    <\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n        <pre><code class=\"language-python\">\ndef sum_n(n):\n    if n == 0:\n        return 0\n    return n + sum_n(n - 1)\n\nprint(sum_n(5))  # 15\n    <\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n        <pre><code class=\"language-java\">\npublic class Main {\n  public static int sum(int n) {\n    if (n == 0) return 0;\n    return n + sum(n - 1);\n  }\n\n  public static void main(String[] args) {\n    System.out.println(sum(5)); \/\/ 15\n  }\n}<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cpp\">\n        <pre><code class=\"language-cpp\">\n#include &lt;iostream&gt;\nusing namespace std;\n\n    int sum(int n) {\n    if (n == 0) return 0;\n    return n + sum(n - 1);\n    }\n\n    int main() {\n    cout << sum(5) << endl; \/\/ 15\n    return 0;\n}\n    <\/code><\/pre>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n        <pre><code class=\"language-c\">\n#include &lt;stdio.h&gt;\n    int sum(int n) {\n    if (n == 0) return 0;\n    return n + sum(n - 1);\n    }\n\n    int main() {\n    printf(\"%d\\n\", sum(5)); \/\/ 15\n    return 0;\n    }\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n        <pre><code class=\"language-csharp\">\nusing System;\nclass Program {\n    static int Sum(int n) {\n        if (n == 0) return 0;\n        return n + Sum(n - 1);\n    }\n    static void Main() {\n        Console.WriteLine(Sum(5)); \/\/ 15\n    }\n}\n  <\/code><\/pre>\n    <\/div>\n<\/div>\n<\/div>\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\n      buttons.forEach((btn) => btn.classList.remove(\"active\"));\n      contents.forEach((content) => content.classList.remove(\"active\"));\n\n      button.classList.add(\"active\");\n      document\n        .querySelector(`.wp_blog_code-tab-content[data-lang=\"${lang}\"]`)\n        .classList.add(\"active\");\n    });\n  });\n\n  const themeToggle = document.getElementById(\"blogNotesThemeToggle\");\n  const themeContainer = document.querySelector(\".wp_blog_theme\");\n\n  themeToggle.addEventListener(\"click\", () => {\n    themeContainer.classList.toggle(\"dark-mode\");\n    themeToggle.textContent =\n      themeContainer.classList.contains(\"dark-mode\") ? \"\u2600\ufe0f\" : \"\ud83c\udf19\";\n  });\n});\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>\ud83c\udf19 Problem Statement: Write a function sum(n) that calculates the sum of the first n natural numbers using recursion. Example: Input: 5 Process: 5 + 4 + 3 + 2 + 1 = 15 Output: 15 Concepts: Recursion: A technique where a function calls itself with a reduced subproblem. Base Case: Stops recursion to prevent<\/p>\n","protected":false},"author":108,"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":[210,322,176,175,211,174,172,173],"tags":[],"class_list":["post-9721","post","type-post","status-publish","format-standard","category-algorithms","category-algorithms-and-data-structures","category-csharp","category-cplusplus","category-data-structures","category-java","category-javascript","category-python"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/9721","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\/108"}],"replies":[{"embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/comments?post=9721"}],"version-history":[{"count":2,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/9721\/revisions"}],"predecessor-version":[{"id":10171,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/9721\/revisions\/10171"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=9721"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=9721"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=9721"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}