{"id":8135,"date":"2025-07-22T10:49:50","date_gmt":"2025-07-22T05:19:50","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=8135"},"modified":"2025-07-22T21:30:30","modified_gmt":"2025-07-22T16:00:30","slug":"first-bad-version","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/first-bad-version\/","title":{"rendered":"First Bad Version"},"content":{"rendered":"\n<!-- Prism.js CSS and JS -->\n<link href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.css\" rel=\"stylesheet\" \/>\n<script src=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/prism.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_code-tabs-container {\n    font-family: \"Segoe UI\", sans-serif !important;\n    max-width: 900px !important;\n    margin: 2rem auto !important;\n    border: 1px solid #ddd !important;\n    border-radius: 8px !important;\n    overflow: hidden !important;\n    background-color: white !important;\n  }\n\n  .wp_blog_code-tabs-header {\n    background: #f7f7f7 !important;\n    display: flex !important;\n    border-bottom: 1px solid #ddd !important;\n  }\n\n  .wp_blog_code-tab-button {\n    flex: 1 !important;\n    padding: 10px 15px !important;\n    border: none !important;\n    background: transparent !important;\n    cursor: pointer !important;\n    font-weight: bold !important;\n    transition: background 0.2s !important;\n    color: #242b33 !important;\n  }\n\n  .wp_blog_code-tab-button.active {\n    background: white !important;\n    border-bottom: 3px solid #0073aa !important;\n  }\n\n  .wp_blog_code-tab-content {\n    display: none !important;\n    padding: 20px !important;\n    background: #242b33 !important;\n  }\n\n  .wp_blog_code-tab-content > pre {\n    background: #242b33 !important;\n  }\n\n  .wp_blog_code-tab-content.active {\n    display: block !important;\n  }\n\n  .wp_blog_code-tab-content pre {\n    margin: 0 !important;\n    overflow-x: auto !important;\n  }\n\n  .wp_blog_explanation {\n    max-width: 900px !important;\n    margin: 2rem auto !important;\n    font-family: \"Segoe UI\", sans-serif !important;\n    line-height: 1.6 !important;\n    background: white !important;\n    color: black !important;\n    padding: 1rem !important;\n    border-radius: 8px !important;\n  }\n\n  .wp_blog_explanation h2 {\n    color: #0073aa !important;\n    font-size: 1.5rem !important;\n    margin-bottom: 0.5rem !important;\n  }\n\n  .wp_blog_explanation code {\n    background: #f1f1f1 !important;\n    padding: 2px 6px !important;\n    border-radius: 4px !important;\n    font-family: monospace !important;\n  }\n\n  .wp_blog_explanation h1,\n  .wp_blog_explanation h2,\n  .wp_blog_explanation h3,\n  .wp_blog_explanation h4,\n  .wp_blog_explanation h5,\n  .wp_blog_explanation h6,\n  .wp_blog_explanation p {\n    margin-top: 10px !important;\n    margin-bottom: 10px !important;\n  }\n<\/style>\n\n\n<div class=\"wp_blog_explanation\">\n  <p>This problem finds the first bad version in a sequence of versions from <code>1<\/code> to <code>n<\/code>. We have an API <code>isBadVersion(version)<\/code> that returns whether a version is bad. We use binary search to pinpoint the earliest bad version.<\/p>\n\n  <h2>Steps<\/h2>\n  <ul>\n    <li>Initialize pointers: <code>l = 1<\/code> and <code>r = n<\/code>.<\/li>\n    <li>While <code>l < r<\/code>:\n      <ul>\n        <li>Compute mid: <code>m = l + floor((r - l) \/ 2)<\/code>.<\/li>\n        <li>If <code>isBadVersion(m)<\/code> is false \u2192 move right (<code>l = m + 1<\/code>).<\/li>\n        <li>Else (true) \u2192 move left or stay (<code>r = m<\/code>).<\/li>\n      <\/ul>\n    <\/li>\n    <li>Loop ends when <code>l == r<\/code>, which is the first bad version.<\/li>\n    <li>Return <code>r<\/code>.<\/li>\n  <\/ul>\n\n  <h2>Dry Run<\/h2>\n  <p><strong>Input:<\/strong> <code>n = 5, bad = 4<\/code><\/p>\n  <ol>\n    <li>l=1, r=5 \u2192 m=3 \u2192 isBad(3)=false \u2192 l=4<\/li>\n    <li>l=4, r=5 \u2192 m=4 \u2192 isBad(4)=true \u2192 r=4<\/li>\n    <li>l==r==4 \u2192 return 4<\/li>\n  <\/ol>\n  <p><strong>Output:<\/strong> <code>4<\/code><\/p>\n\n  <p><strong>Input:<\/strong> <code>n = 1, bad = 1<\/code><\/p>\n  <ol>\n    <li>l=1, r=1 \u2192 no loop \u2192 return 1<\/li>\n  <\/ol>\n  <p><strong>Output:<\/strong> <code>1<\/code><\/p>\n\n  <h2>Time & Space Complexity<\/h2>\n  <ul>\n    <li><strong>Time Complexity:<\/strong> O(log\u202fn)<\/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=\"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=\"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=\"c#\">C#<\/button>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n    <pre><code class=\"language-javascript\">\nvar solution = function(isBadVersion) {\n    return function(n) {\n        let l = 1;\n        let r = n;\n        while (l < r) {\n            let m = l + Math.floor((r - l) \/ 2);\n            if (!isBadVersion(m)) {\n                l = m + 1;\n            } else {\n                r = m;\n            }\n        }\n        return r;\n    };\n};\n    <\/code><\/pre>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"cpp\">\n    <pre><code class=\"language-cpp\">\nclass Solution {\npublic:\n    int firstBadVersion(int n) {\n        int l = 1, r = n;\n        while (l < r) {\n            int m = l + (r - l) \/ 2;\n            if (!isBadVersion(m)) l = m + 1;\n            else r = m;\n        }\n        return r;\n    }\n};\n    <\/code><\/pre>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n    <pre><code class=\"language-c\">\nint firstBadVersion(int n) {\n    int l = 1, r = n;\n    while (l < r) {\n        int m = l + (r - l) \/ 2;\n        if (!isBadVersion(m)) l = m + 1;\n        else r = m;\n    }\n    return r;\n}\n    <\/code><\/pre>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n    <pre><code class=\"language-java\">\npublic class Solution {\n    public int firstBadVersion(int n) {\n        int l = 1, r = n;\n        while (l < r) {\n            int m = l + (r - l) \/ 2;\n            if (!isBadVersion(m)) l = m + 1;\n            else r = m;\n        }\n        return r;\n    }\n}\n    <\/code><\/pre>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n    <pre><code class=\"language-python\">\ndef firstBadVersion(n):\n    l, r = 1, n\n    while l < r:\n        m = l + (r - l) \/\/ 2\n        if not isBadVersion(m):\n            l = m + 1\n        else:\n            r = m\n    return r\n    <\/code><\/pre>\n  <\/div>\n\n  <div class=\"wp_blog_code-tab-content\" data-lang=\"c#\">\n    <pre><code class=\"language-c#\">\npublic class Solution {\n    public int FirstBadVersion(int n) {\n        int l = 1, r = n;\n        while (l < r) {\n            int m = l + (r - l) \/ 2;\n            if (!IsBadVersion(m)) l = m + 1;\n            else r = m;\n        }\n        return r;\n    }\n}\n    <\/code><\/pre>\n  <\/div>\n<\/div>\n\n\n<a href=\"https:\/\/leetcode.com\/problems\/first-bad-version\/description\/\" target=\"blank\">Solve this problem.<\/a>\n<script>\n  document.addEventListener(\"DOMContentLoaded\", function () {\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        button.classList.add(\"active\");\n\n        contents.forEach((content) => {\n          content.classList.toggle(\"active\", content.getAttribute(\"data-lang\") === lang);\n        });\n      });\n    });\n  });\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>This problem finds the first bad version in a sequence of versions from 1 to n. We have an API isBadVersion(version) that returns whether a version is bad. We use binary search to pinpoint the earliest bad version. Steps Initialize pointers: l = 1 and r = n. While l < r: Compute mid: m\n<\/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":[322,176,175,211,174,172,173],"tags":[],"class_list":["post-8135","post","type-post","status-publish","format-standard","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\/8135","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=8135"}],"version-history":[{"count":1,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/8135\/revisions"}],"predecessor-version":[{"id":8136,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/8135\/revisions\/8136"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=8135"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=8135"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=8135"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}