{"id":10100,"date":"2025-09-22T21:02:53","date_gmt":"2025-09-22T15:32:53","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=10100"},"modified":"2025-09-23T21:02:20","modified_gmt":"2025-09-23T15:32:20","slug":"candy-one-pass-o1-space","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/candy-one-pass-o1-space\/","title":{"rendered":"Candy One Pass O(1) Space"},"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>\n      There are <code>n<\/code> children standing in a line. Each child is assigned a rating value given in the integer array <code>ratings<\/code>.\n    <\/p>\n\n    <ul>You are giving candies to these children subjected to the following requirements:\n      <li>Each child must have at least one candy.<\/li>\n      <li>Children with a higher rating get more candies than their neighbors.<\/li>\n    <\/ul>\n\n    <p>\n      Return <i>the minimum number of candies you need to have to distribute the candies to the children<\/i>.\n    <\/p>\n    <h3>Example 1:<\/h2>\n    <p><strong>Input:<\/strong> trips = [[2,1,5],[3,3,7]], capacity = 4<\/p>\n    <p><strong>Output:<\/strong> false<\/p>\n\n    <p>\n      Return <i>the minimum number of candies you need to have to distribute the candies to the children<\/i>.\n    <\/p>\n    \n    \n    <h3>Example 1:<\/h2>\n    <p><strong>Input:<\/strong> ratings = [1,0,2]<\/p>\n    <p><strong>Output:<\/strong> 5<\/p>\n    <p><strong>Explanation:<\/strong> You can allocate to the first, second and third child with 2, 1, 2 candies respectively.<\/p>\n\n        <h3>Example 2:<\/h2>\n    <p><strong>Input:<\/strong> ratings = [1,2,2]<\/p>\n    <p><strong>Output:<\/strong> 4<\/p>\n    <p><strong>Explanation:<\/strong> You can allocate to the first, second and third child with 1, 2, 1 candies respectively.\nThe third child gets 1 candy because it satisfies the above two conditions.<\/p>\n\n    <h3>Constraints<\/h3>\n    <ul>\n        <li><code>n == ratings.length<\/code><\/li>\n        <li><code>1 <= n <= 2 * 10<sup>4<\/sup><\/code><\/li>\n        <li><code>0 <= ratings[i] <= 2 * 10<sup>4<\/sup><\/code><\/li>\n    <\/ul>\n    \n<h2>Approach:<\/h2>\n   <ul>\n    <li>Every child must get at least <strong>1 candy \u2192 start<\/strong> with <code>ans = n<\/code>.<\/li>\n    <li><strong>Traverse<\/strong> the ratings array and look for <code>increasing and decreasing slopes<\/code>.\n        <ul>\n            <li><strong>Increasing slope (up)<\/strong>: When <code>arr[i] > arr[i-1]<\/code>, keep incrementing up. Add candies accordingly.<\/li>\n            <li><strong>Decreasing slope (down)<\/strong>: When <code>arr[i] < arr[i-1]<\/code>, keep incrementing down. Add candies accordingly.<\/li>\n        <\/ul>\n    <\/li>\n    <li>To avoid <strong>double-counting<\/strong> the peak (where up and down meet), <code>subtract Math.min(up, down)<\/code>.<\/li>\n    <li>Continue until the end and <strong>return ans<\/strong>.<\/li>\n   <\/ul>\n\n    <h2>Time & Space Complexity:<\/h2>\n    <p><strong>Time Complexity:<\/strong> <code>O(n)<\/code><\/p>\n    <p><strong>Space Complexity:<\/strong> <code>O(1)<\/code><\/p>\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>arr = [1, 0, 2]<\/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);\">\n\nStep 0: Start Function: candy(arr)\narr = [1, 0, 2]\nn = 3\nans = n = 3\ni = 1\n\nIteration (i = 1):\n- Check arr[1] === arr[0] \u2192 0 === 1 ? false\n- up = 0\n- Increasing slope? while(i < 3 &#038;&#038; arr[i] > arr[i-1]) \u2192 0 > 1 ? false\n- down = 0\n- Decreasing slope? i=1, arr[1]=0, arr[0]=1 \u2192 0 < 1 \u2192 true\n  \u2192 down = 1, ans = 4, i = 2\n- Next check: arr[2]=2, arr[1]=0 \u2192 2 < 0 ? false\n- Update ans = 4 - min(up, down) = 4 - min(0,1) = 4\n\nIteration (i = 2):\n- Check arr[2] === arr[1] \u2192 2 === 0 ? false\n- up = 0\n- Increasing slope? i=2, arr[2]=2, arr[1]=0 \u2192 2 > 0 \u2192 true\n  \u2192 up = 1, ans = 5, i = 3\n- Loop ends (i == n)\n- down = 0 (no check, since i = n)\n- Update ans = 5 - min(up, down) = 5 - min(1,0) = 5\n\nStep 3: End\nReturn ans = 5\n  <\/pre> \n  \n  <p><strong>Output:<\/strong> <code>5<\/code><\/p> \n<\/div>\n\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\">\nvar candy = function(arr) {\n    let n = arr.length;\n    let ans = n;\n    let i = 1;\n\n    while(i < n){\n        if(arr[i] === arr[i-1]) {\n            ++i;\n            continue;\n        }\n        let up = 0;\n        while(i < n &#038;&#038; arr[i] > arr[i-1]){\n            ++up;\n            ans = ans + up;\n            ++i;\n        }\n        let down = 0;\n        while(i < n &#038;&#038; arr[i] < arr[i-1]) {\n            ++down;\n            ans += down;\n            ++i;\n        }\n        ans = ans - Math.min(up, down);\n    }\n    return ans;\n};\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n      <pre><code class=\"language-python\">\ndef candy(arr):\n    n = len(arr)\n    ans = n\n    i = 1\n    while i < n:\n        if arr[i] == arr[i-1]:\n            i += 1\n            continue\n        up = 0\n        while i < n and arr[i] > arr[i-1]:\n            up += 1\n            ans += up\n            i += 1\n        down = 0\n        while i < n and arr[i] < arr[i-1]:\n            down += 1\n            ans += down\n            i += 1\n\n        ans -= min(up, down)\n    return ans\n      <\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"java\">\n      <pre><code class=\"language-java\">\npublic class Solution {\n    public static long candy(int[] arr) {\n        int n = arr.length;\n        long ans = n;\n        int i = 1;\n        while (i < n) {\n            if (arr[i] == arr[i - 1]) { ++i; continue; }\n            int up = 0;\n            while (i < n &#038;&#038; arr[i] > arr[i - 1]) {\n                ++up;\n                ans += up;\n                ++i;\n            }\n            int down = 0;\n            while (i < n &#038;&#038; arr[i] < arr[i - 1]) {\n                ++down;\n                ans += down;\n                ++i;\n            }\n            ans -= Math.min(up, down);\n        }\n        return ans;\n    }\n    public static void main(String[] args) {\n        int[] ratings = {1, 2, 2};\n        System.out.println(candy(ratings)); \/\/ expected 4\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\">\n<!-- #include &lt;vector&gt; -->\n#include &lt;bits\/stdc++.h&gt;\nusing namespace std;\n\nlong long candy(const vector<int>& arr) {\n    int n = arr.size();\n    long long ans = n;\n    int i = 1;\n    while (i < n) {\n        if (arr[i] == arr[i-1]) { ++i; continue; }\n        int up = 0;\n        while (i < n &#038;&#038; arr[i] > arr[i-1]) {\n            ++up;\n            ans += up;\n            ++i;\n        }\n        int down = 0;\n        while (i < n &#038;&#038; arr[i] < arr[i-1]) {\n            ++down;\n            ans += down;\n            ++i;\n        }\n        ans -= min(up, down);\n    }\n    return ans;\n}\nint main() {\n    vector<int> ratings = {1, 2, 2};\n    cout << candy(ratings) << endl; \n    return 0;\n}\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"c\">\n      <pre><code class=\"language-c\">\n#include &lt;stdio.h&gt;\n\nlong candy(int arr[], int n) {\n    long ans = n;\n    int i = 1;\n    while (i < n) {\n        if (arr[i] == arr[i-1]) { ++i; continue; }\n        int up = 0;\n        while (i < n &#038;&#038; arr[i] > arr[i-1]) {\n            ++up;\n            ans += up;\n            ++i;\n        }\n        int down = 0;\n        while (i < n &#038;&#038; arr[i] < arr[i-1]) {\n            ++down;\n            ans += down;\n            ++i;\n        }\n        ans -= (up < down ? up : down);\n    }\n    return ans;\n}\nint main() {\n    int ratings[] = {1, 2, 2};\n    int n = sizeof(ratings) \n    printf(\"%ld\\n\", candy(ratings, n)); \n    return 0;\n}\n\n <\/code><\/pre>\n    <\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n      <pre><code class=\"language-csharp\">\nusing System;\nclass Solution {\n    public static long Candy(int[] arr) {\n        int n = arr.Length;\n        long ans = n;\n        int i = 1;\n        while (i < n) {\n            if (arr[i] == arr[i - 1]) { ++i; continue; }\n            int up = 0;\n            while (i < n &#038;&#038; arr[i] > arr[i - 1]) {\n                ++up;\n                ans += up;\n                ++i;\n            }\n            int down = 0;\n            while (i < n &#038;&#038; arr[i] < arr[i - 1]) {\n                ++down;\n                ans += down;\n                ++i;\n            }\n            ans -= Math.Min(up, down);\n        }\n        return ans;\n    }\n    static void Main() {\n        int[] ratings = {1, 2, 2};\n        Console.WriteLine(Candy(ratings)); \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: There are n children standing in a line. Each child is assigned a rating value given in the integer array ratings. You are giving candies to these children subjected to the following requirements: Each child must have at least one candy. Children with a higher rating get more candies than their neighbors.<\/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":[210,260,176,175,211,811,810,174,172,173],"tags":[],"class_list":["post-10100","post","type-post","status-publish","format-standard","category-algorithms","category-c-c-plus-plus","category-csharp","category-cplusplus","category-data-structures","category-data-structures-and-algorithms","category-dsa","category-java","category-javascript","category-python"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/10100","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=10100"}],"version-history":[{"count":2,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/10100\/revisions"}],"predecessor-version":[{"id":10102,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/10100\/revisions\/10102"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=10100"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=10100"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=10100"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}