{"id":7186,"date":"2025-06-25T15:46:18","date_gmt":"2025-06-25T10:16:18","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7186"},"modified":"2025-09-29T18:36:04","modified_gmt":"2025-09-29T13:06:04","slug":"removeduplicatesfromsortedarray","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/removeduplicatesfromsortedarray\/","title":{"rendered":"Remove Duplicates from Sorted Array"},"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_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;   \/* light bg instead of dark blue *\/\n  color: #E58C32;        \/* brand orange *\/\n  padding: 3px 6px;\n  border-radius: 4px;\n  font-family: 'Courier New', monospace;\n  font-weight: 600;      \/* optional, makes it pop *\/\n}\n\n.wp_blog_explanation img {\n  max-width: 100%;\n  border-radius: var(--tab-radius);\n  margin-top: 1rem;\n  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);\n}\n\n\/* Tab Buttons *\/\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 var(--primary);\n  background: white;\n  color: var(--primary);\n  border-radius: 50px;\n  font-weight: 600;\n  cursor: pointer;\n  transition: all 0.3s ease;\n}\n\n.wp_blog_code-tab-button:hover {\n  background: var(--secondary);\n}\n\n.wp_blog_code-tab-button.active {\n  background: var(--primary);\n  color: white;\n}\n\n\/* Code Content *\/\n.wp_blog_code-tab-content {\n  display: none;\n  background: var(--code-bg);\n  border-radius: var(--tab-radius);\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  background: var(--code-bg);\n  border-radius: var(--tab-radius);\n  color: var(--code-text);\n}\n\n\/* Dark mode variables *\/\n.wp_blog_theme.dark-mode {\n  --light-bg: #121212;\n  --text-dark: #f5f5f5;\n  --shadow: 0 4px 12px rgba(255, 255, 255, 0.08);\n  --code-bg: #1e1e1e;\n  --code-text: #c5f0ff;\n}\n\n.wp_blog_theme.dark-mode .wp_blog_explanation {\n  background: #1e1e1e;\n}\n\n\/* Dark mode code highlight *\/\n.wp_blog_theme.dark-mode .wp_blog_explanation code {\n  background: #333;\n  color: #ffd27f;\n}\n\n.wp_blog_theme {\n  position: relative; \/* 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>Given an integer array <code>nums<\/code> sorted in <code>non-decreasing order<\/code>, remove the duplicates <code>in-place<\/code> such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums.<\/p>\n<br\/>\n        <p>Consider the number of unique elements of <code>nums<\/code> to be <code>k<\/code>. To get accepted, you need to do the following things:<\/p>\n\n        <p>Change the array <code>nums<\/code> such that the first <code>k<\/code> elements of <code>nums<\/code> contain the unique elements in the order they were present in <code>nums<\/code> initially.\n        The remaining elements of <code>nums<\/code> are not important, as well as the size of <code>nums<\/code>.\n        eturn k.<\/p>\n\n\n                <h2>Examples:<\/h2>\n\n                <h5>Example 1:<\/h5>\n                <p><strong>Input:<\/strong> nums = [1,1,2]<\/p>\n                <p><strong>Output:<\/strong> 2, nums = [1,2,_] <\/p>\n                <p>\n                  <code>Explanation:<\/code>\n                  Your function should return k = 2, with the first two elements of nums being 1 and 2 \n                  respectively.\n                  \n                  It does not matter what you leave beyond the returned k (hence they are underscores).\n                <\/p>\n\n                <h5>Example 2:<\/h5>\n                <p><strong>Input:<\/strong> nums = [0,0,1,1,1,2,2,3,3,4]<\/p>\n                <p><strong>Output:<\/strong> 5, nums = [0,1,2,3,4,_,_,_,_,_] <\/p>\n                <p>\n                  <code>Explanation:<\/code> Your function should return k = 5, with the first five elements of nums being 0, 1, 2, 3, and \n                  4 respectively.\n                  \n                  It does not matter what you leave beyond the returned k (hence they are underscores).\n                <\/p>\n        \n                <h2>Constraints:<\/h2>\n                <p>1 &le; <code>nums.length<\/code> &le; 3 * 10<sup>4<\/sup><\/p>\n                <p>-100 &le; <code>nums[i]<\/code> &le; 100<\/p>\n                <p>nums is sorted in non-decreasing order.<\/p>\n\n                <h2>Important Points:<\/h2>\n                <p><strong>Non-decreasing order:<\/strong><\/p>\n                <p>\n                  The array is sorted such that elements can stay the same or increase: <code>nums[i] <= nums[i+1]<\/code>.\n                <\/p>\n                <p><strong>Examples:<\/strong><\/p>\n                <p> Valid: <code>[1, 1, 2, 3, 3, 5]<\/code> <\/p>\n                <p> Invalid: <code>[3, 2, 1] <\/code>(this is decreasing).<\/p>\n\n                <p><strong>In-place:<\/strong><\/p>\n\n                <p>You must modify the given <code>nums<\/code> array itself.<\/p>\n                <p>You are <strong>not allowed<\/strong> to use extra arrays for storing the result.<\/p>\n\n                <h2>Approach:<\/h2>\n                <ul>\n                    <li><code>x = 0:<\/code>Pointer to track the last unique element's position.<\/li>\n                    <li>Loop through the array from <code>i = 0<\/code>to<code>nums.length<\/code>.<\/li>\n                    <li>If true (new unique value), increment <code>x<\/code> and update <code>nums[x] = nums[i]<\/code>.<\/li>\n                    <li>This shifts the unique value forward in the array.<\/li>\n                    <li>At the end, <code>x + 1<\/code> gives the count of unique elements.<\/li>\n                <\/ul>\n\n                <h2>Time Complexity:<\/h2>\n                <li>\n                  <p>The function uses a single loop that iterates through the entire array once.<\/p>\n                  <p>Each iteration performs constant-time operations (comparisons and assignments).<\/p>\n                  <p><strong>Time Complexity = O(n)<\/strong>, where <code>n = nums.length<\/code>.<\/p>\n                <\/li>\n                <h2>Space Complexity:<\/h2>\n                <li>\n                  <p>The function modifies the array <strong>in-place<\/strong>.<\/p>\n                  <p>Uses only a few extra variables:<code>x<\/code>and<code>i<\/code>.<\/p>\n                  <p><strong>Space Complexity = O(1)<\/strong>(constant extra space).<\/p>\n                <\/li>\n\n\n<h2>Dry Run<\/h2>\n<div style=\"background: var(--light-bg); border-left: 4px solid var(--primary); padding: 1rem; border-radius: var(--tab-radius); margin: 1rem 0; color: var(--text-dark);\"> \n  <p><strong>Input:<\/strong> <code>[1, 1, 2, 3, 3, 5]<\/code><\/p> \n  \n  <pre style=\"white-space: pre-wrap; background: var(--code-bg); padding: 1rem; border-radius: 8px; overflow-x: auto; color: var(--code-text);\">\nInitial state: \n  x = 0 \n\ni = 0: nums[i] = 1, nums[x] = 1 \u2192 NOT greater \u2192 skip\ni = 1: nums[i] = 1, nums[x] = 1 \u2192 NOT greater \u2192 skip\ni = 2: nums[i] = 2, nums[x] = 1 \u2192 GREATER \u2192 x=1, nums[1] = 2\ni = 3: nums[i] = 3, nums[x] = 2 \u2192 GREATER \u2192 x=2, nums[2] = 3\ni = 4: nums[i] = 3, nums[x] = 3 \u2192 NOT greater \u2192 skip\ni = 5: nums[i] = 5, nums[x] = 3 \u2192 GREATER \u2192 x=3, nums[3] = 5\n\nFinal array: [1, 2, 3, 5, 3, 5]\nUnique count: x + 1 = 4\n  <\/pre> \n  \n  <p><strong>Output:<\/strong> <code>4<\/code> (First 4 elements are unique: [1, 2, 3, 5])<\/p> \n<\/div>\n\n        <h2>Visualisation:<\/h2>\n        <img decoding=\"async\" src=\"https:\/\/namastedev.com\/blog\/wp-content\/uploads\/2025\/06\/Screenshot-2025-06-25-at-3.20.41\u202fPM.png\" alt=\"Remove duplicates\" \/>\n    <\/div>\n\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=\"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\">\n var removeDuplicates = function(nums) {\n      let x = 0;\n      for (let i = 0; i < nums.length; i++) {\n          if (nums[i] > nums[x]) {\n              x++;\n              nums[x] = nums[i];\n          }\n      }\n      return x + 1;\n  }; \n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n      <pre><code class=\"language-python\">\nclass Solution(object):\n      def removeDuplicates(self, nums):\n          x = 0\n          for i in range(len(nums)):\n              if nums[i] > nums[x]:\n                  x += 1\n                  nums[x] = nums[i]\n          return x + 1\n      <\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n      <pre><code class=\"language-java\">\n public class Solution {\n      public int removeDuplicates(int[] nums) {\n          int x = 0;\n          for (int i = 0; i < nums.length; i++) {\n              if (nums[i] > nums[x]) {\n                  x++;\n                  nums[x] = nums[i];\n              }\n          }\n          return x + 1;\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 {\n  public:\n      int removeDuplicates(vector<int>& nums) {\n          int x = 0;\n          for (int i = 0; i < nums.size(); i++) {\n              if (nums[i] > nums[x]) {\n                  x++;\n                  nums[x] = nums[i];\n              }\n          }\n          return x + 1;\n      }\n  }; \n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n      <pre><code class=\"language-c\">\n int removeDuplicates(int* nums, int numsSize) {\n      int x = 0;\n      for (int i = 0; i < numsSize; i++) {\n          if (nums[i] > nums[x]) {\n              x++;\n              nums[x] = nums[i];\n          }\n      }\n      return x + 1;\n  }\n <\/code><\/pre>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n      <pre><code class=\"language-csharp\">\npublic class Solution {\n          public int RemoveDuplicates(int[] nums) {\n              if (nums.Length == 0) return 0;\n      \n              int x = 0;\n              for (int i = 1; i < nums.Length; i++) {\n                  if (nums[i] > nums[x]) {\n                      x++;\n                      nums[x] = nums[i];\n                  }\n              }\n              return x + 1;\n          }\n      } \n      <\/code><\/pre>\n    <\/div>\n  <\/div>\n<\/div>\n\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\n","protected":false},"excerpt":{"rendered":"<p>\ud83c\udf19 Problem Statement: Given an integer array nums sorted in non-decreasing order, remove the duplicates in-place such that each unique element appears only once. The relative order of the elements should be kept the same. Then return the number of unique elements in nums. Consider the number of unique elements of nums to be k.<\/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":[210,322,260,176,175,212,211,811,810,174,172,173,284],"tags":[],"class_list":["post-7186","post","type-post","status-publish","format-standard","category-algorithms","category-algorithms-and-data-structures","category-c-c-plus-plus","category-csharp","category-cplusplus","category-code-optimization","category-data-structures","category-data-structures-and-algorithms","category-dsa","category-java","category-javascript","category-python","category-software-engineering"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7186","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=7186"}],"version-history":[{"count":8,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7186\/revisions"}],"predecessor-version":[{"id":10155,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7186\/revisions\/10155"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7186"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7186"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7186"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}