{"id":7478,"date":"2025-07-02T15:05:58","date_gmt":"2025-07-02T09:35:58","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7478"},"modified":"2025-07-02T15:07:35","modified_gmt":"2025-07-02T09:37:35","slug":"valid-palindrome-approach-1-extra-space","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/valid-palindrome-approach-1-extra-space\/","title":{"rendered":"Valid Palindrome | Approach 1 Extra Space"},"content":{"rendered":"\n<!-- Prism.js CSS and JS -->\n<link\n  href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.css\"\n  rel=\"stylesheet\"\n\/>\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<div class=\"wp_blog_explanation\">\n  <p>\n    The goal of this problem is to determine whether a given string is a\n    palindrome, considering only alphanumeric characters and ignoring cases. A\n    palindrome reads the same forward and backward after removing\n    non-alphanumeric characters.\n  <\/p>\n\n  <h2>Steps<\/h2>\n  <ul>\n    <li>\n      Convert the string to lowercase to ensure case-insensitive comparison.\n    <\/li>\n    <li>Traverse each character in the string.<\/li>\n    <li>Keep only alphanumeric characters using ASCII code checks.<\/li>\n    <li>Build a filtered version and its reverse simultaneously.<\/li>\n    <li>Return true if both strings are equal, else return false.<\/li>\n  <\/ul>\n\n  <h2>Dry Run<\/h2>\n  <p><strong>Input:<\/strong> <code>s = \"Race a Car\"<\/code><\/p>\n  <ol>\n    <li>Lowercase: <code>\"race a car\"<\/code><\/li>\n    <li>Filtered alphanumerics: <code>\"raceacar\"<\/code><\/li>\n    <li>Reverse: <code>\"racacear\"<\/code><\/li>\n    <li>\n      Since <code>\"raceacar\"<\/code> \u2260 <code>\"racacear\"<\/code>, return\n      <code>false<\/code>\n    <\/li>\n  <\/ol>\n\n  <h2>Time &#038; Space Complexity<\/h2>\n  <ul>\n    <li>\n      <strong>Time Complexity:<\/strong> O(n), where n is the length of the input\n      string\n    <\/li>\n    <li>\n      <strong>Space Complexity:<\/strong> O(n), due to additional filtered and\n      reversed strings\n    <\/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\">\n      JavaScript\n    <\/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  <\/div>\n\n  <!-- JavaScript -->\n  <div class=\"wp_blog_code-tab-content active\" data-lang=\"js\">\n    <pre><code class=\"language-javascript\">\nvar isPalindrome = function (s) {\ns = s.toLowerCase();\nlet filteredString = \"\";\nlet rev = \"\";\nfor (let i = 0; i < s.length; i++) {\n    if (\n    (s[i].charCodeAt() >= \"a\".charCodeAt() && s[i].charCodeAt() <= \"z\".charCodeAt()) ||\n    (s[i].charCodeAt() >= \"0\".charCodeAt() && s[i].charCodeAt() <= \"9\".charCodeAt())\n    ) {\n    filteredString = filteredString + s[i];\n    rev = s[i] + rev;\n    }\n}\nreturn filteredString === rev;\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\">\n#include &lt;iostream&gt;\n#include &lt;cctype&gt;\nusing namespace std;\n\nbool isPalindrome(string s) {\n    string filtered = \"\", rev = \"\";\n    for (char c : s) {\n        if (isalnum(c)) {\n            char lower = tolower(c);\n            filtered += lower;\n            rev = lower + rev;\n        }\n    }\n    return filtered == rev;\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\">\n#include &lt;stdio.h&gt;\n#include &lt;ctype.h&gt;\n#include &lt;string.h&gt;\n\nint isPalindrome(char* s) {\n    char filtered[1000] = \"\", rev[1000] = \"\";\n    int fIdx = 0, rIdx = 0;\n\n    for (int i = 0; s[i]; i++) {\n        if (isalnum(s[i])) {\n            char c = tolower(s[i]);\n            filtered[fIdx++] = c;\n        }\n    }\n\n    for (int i = fIdx - 1; i >= 0; i--) {\n        rev[rIdx++] = filtered[i];\n    }\n\n    filtered[fIdx] = '\\0';\n    rev[rIdx] = '\\0';\n\n    return strcmp(filtered, rev) == 0;\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\">\npublic class Solution {\n    public boolean isPalindrome(String s) {\n        StringBuilder filtered = new StringBuilder();\n        StringBuilder rev = new StringBuilder();\n        for (char c : s.toCharArray()) {\n            if (Character.isLetterOrDigit(c)) {\n                char lower = Character.toLowerCase(c);\n                filtered.append(lower);\n                rev.insert(0, lower);\n            }\n        }\n        return filtered.toString().equals(rev.toString());\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\">\ndef isPalindrome(s: str) -> bool:\n    filtered = \"\"\n    rev = \"\"\n    for c in s:\n        if c.isalnum():\n            c = c.lower()\n            filtered += c\n            rev = c + rev\n    return filtered == rev\n      <\/code><\/pre>\n  <\/div>\n<\/div>\n\n<a href=\"https:\/\/leetcode.com\/problems\/two-sum\/description\/\" target=\"blank\"\n  >Solve this problem.<\/a\n>\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(\n            \"active\",\n            content.getAttribute(\"data-lang\") === lang\n          );\n        });\n      });\n    });\n  });\n<\/script>\n\n","protected":false},"excerpt":{"rendered":"<p>The goal of this problem is to determine whether a given string is a palindrome, considering only alphanumeric characters and ignoring cases. A palindrome reads the same forward and backward after removing non-alphanumeric characters. Steps Convert the string to lowercase to ensure case-insensitive comparison. Traverse each character in the string. Keep only alphanumeric characters using<\/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":[1],"tags":[],"class_list":{"0":"post-7478","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-uncategorized"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7478","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=7478"}],"version-history":[{"count":2,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7478\/revisions"}],"predecessor-version":[{"id":7492,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7478\/revisions\/7492"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7478"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7478"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7478"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}