{"id":7497,"date":"2025-07-02T15:19:45","date_gmt":"2025-07-02T09:49:45","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7497"},"modified":"2025-07-22T21:39:05","modified_gmt":"2025-07-22T16:09:05","slug":"group-anagrams-approach-2-hashed-key","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/group-anagrams-approach-2-hashed-key\/","title":{"rendered":"Group Anagrams &#8211; Approach 2 &#8211; Hashed Key"},"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\n\n<div class=\"wp_blog_explanation\">\n    <p>\n      Instead of sorting the string, this approach creates a unique hash key for each string based on the frequency of characters. This improves performance by avoiding costly sort operations for every string.\n    <\/p>\n  \n    <h2>Steps<\/h2>\n    <ul>\n      <li>Initialize a hashmap to store grouped anagrams.<\/li>\n      <li>For each word in the input array:<\/li>\n      <ul>\n        <li>Create an array of size 26 to count frequency of each letter.<\/li>\n        <li>Convert that frequency array into a unique string key (like &#8220;#1#0#2&#8230;&#8221;).<\/li>\n      <\/ul>\n      <li>Use this string as a hash key to group anagrams.<\/li>\n      <li>Return all the grouped values.<\/li>\n    <\/ul>\n  \n    <h2>Dry Run<\/h2>\n    <p><strong>Input:<\/strong> <code>[\"eat\", \"tea\", \"tan\", \"ate\", \"nat\", \"bat\"]<\/code><\/p>\n    <ol>\n      <li><code>\"eat\"<\/code> \u2192 freq = <code>[1,0,0,...,1,1,...]<\/code> \u2192 key = &#8220;#1#0#0#0&#8230;#1#1&#8221;<\/li>\n      <li>All anagrams like &#8220;tea&#8221; and &#8220;ate&#8221; will have the same key.<\/li>\n      <li>Final groups: <code>[[\"eat\",\"tea\",\"ate\"],[\"tan\",\"nat\"],[\"bat\"]]<\/code><\/li>\n    <\/ol>\n  \n    <h2>Time &#038; Space Complexity<\/h2>\n    <ul>\n      <li><strong>Time Complexity:<\/strong> O(n\u00b7k), where n = number of strings, k = average length of strings (no sorting)<\/li>\n      <li><strong>Space Complexity:<\/strong> O(n\u00b7k), for storing frequency map and result<\/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=\"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\">\n  var groupAnagrams = function(strs) {\n      let map = {};\n  \n      for (let i = 0; i &lt; strs.length; i++) {\n          let freqArr = Array(26).fill(0);\n          let s = strs[i];\n  \n          for (let j = 0; j &lt; s.length; j++) {\n              let index = s[j].charCodeAt(0) - 'a'.charCodeAt(0);\n              freqArr[index]++;\n          }\n  \n          let key = \"\";\n          for (let k = 0; k &lt; 26; k++) {\n              key += \"#\" + freqArr[k];\n          }\n  \n          if (!map[key]) {\n              map[key] = [s];\n          } else {\n              map[key].push(s);\n          }\n      }\n  \n      return Object.values(map);\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;vector&gt;\n  #include &lt;unordered_map&gt;\n  #include &lt;string&gt;\n  using namespace std;\n  \n  vector&lt;vector&lt;string&gt;&gt; groupAnagrams(vector&lt;string&gt;& strs) {\n      unordered_map&lt;string, vector&lt;string&gt;&gt; map;\n  \n      for (string s : strs) {\n          vector&lt;int&gt; freq(26, 0);\n          for (char c : s) {\n              freq[c - 'a']++;\n          }\n  \n          string key;\n          for (int count : freq) {\n              key += \"#\" + to_string(count);\n          }\n  \n          map[key].push_back(s);\n      }\n  \n      vector&lt;vector&lt;string&gt;&gt; result;\n      for (auto it : map) {\n          result.push_back(it.second);\n      }\n  \n      return result;\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\">\n  import java.util.*;\n  \n  public class Solution {\n      public List&lt;List&lt;String&gt;&gt; groupAnagrams(String[] strs) {\n          Map&lt;String, List&lt;String&gt;&gt; map = new HashMap&lt;&gt;();\n  \n          for (String s : strs) {\n              int[] freq = new int[26];\n              for (char c : s.toCharArray()) {\n                  freq[c - 'a']++;\n              }\n  \n              StringBuilder key = new StringBuilder();\n              for (int count : freq) {\n                  key.append(\"#\").append(count);\n              }\n  \n              map.computeIfAbsent(key.toString(), k -&gt; new ArrayList&lt;&gt;()).add(s);\n          }\n  \n          return new ArrayList&lt;&gt;(map.values());\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  from collections import defaultdict\n  \n  def groupAnagrams(strs):\n      anagram_map = defaultdict(list)\n  \n      for s in strs:\n          freq = [0] * 26\n          for char in s:\n              freq[ord(char) - ord('a')] += 1\n          key = tuple(freq)\n          anagram_map[key].append(s)\n  \n      return list(anagram_map.values())\n      <\/code><\/pre>\n    <\/div>\n  <\/div>\n  \n\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>Instead of sorting the string, this approach creates a unique hash key for each string based on the frequency of characters. This improves performance by avoiding costly sort operations for every string. Steps Initialize a hashmap to store grouped anagrams. For each word in the input array: Create an array of size 26 to count<\/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-7497","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\/7497","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=7497"}],"version-history":[{"count":1,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7497\/revisions"}],"predecessor-version":[{"id":7499,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7497\/revisions\/7499"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7497"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7497"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7497"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}