{"id":7778,"date":"2025-07-11T15:01:37","date_gmt":"2025-07-11T09:31:37","guid":{"rendered":"https:\/\/namastedev.com\/blog\/?p=7778"},"modified":"2025-07-12T11:29:21","modified_gmt":"2025-07-12T05:59:21","slug":"next-greater-element-ii","status":"publish","type":"post","link":"https:\/\/namastedev.com\/blog\/next-greater-element-ii\/","title":{"rendered":"Next Greater Element II"},"content":{"rendered":"\n<!-- Next Greater Element II -->\n<link\n    href=\"https:\/\/cdn.jsdelivr.net\/npm\/prismjs@1.29.0\/themes\/prism-tomorrow.min.css\"\n    rel=\"stylesheet\"\n\/>\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: #f8c291;\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    \/* 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    .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    .wp_blog_explanation code {\n        background: #fef9f4;\n        padding: 3px 6px;\n        border-radius: 4px;\n        font-family: \"Courier New\", monospace;\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    .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    .wp_blog_code-tab-button:hover {\n        background: var(--secondary);\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    .wp_blog_code-tab-content.active {\n        display: block;\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<\/style>\n\n<div class=\"wp_blog_container wp_blog_theme\">\n<h1 class=\"wp_blog_main-heading\"><\/h1>\n\n<div class=\"wp_blog_explanation\">\n    <h2>Problem Statement:<\/h2>\n    <p>\n        Given a circular integer array <code>nums<\/code> (i.e., the next element of <code>nums[nums.length - 1]<\/code> is <code>nums[0]<\/code>), return the <code>next greater number<\/code> for every element in <code>nums<\/code>.\n    <\/p>\n    <p>\n        The <strong>next greater number<\/strong> of a number <code>x<\/code> is the first greater number to its traversing-order next in the array, which means you could search circularly to find its next greater number. If it doesn&#8217;t exist, return <code>-1<\/code> for this number.\n    <\/p>\n\n    <h2>Examples:<\/h2>\n    <p><strong>Example 1:<\/strong><\/p>\n    <p><strong>Input:<\/strong><\/p>\n        <p>nums = [1,2,1]<\/p>\n    <p><strong>Output:<\/strong><code> [2,-1,2]<\/code><\/p>\n    <p><strong>Explanation:<\/strong>The first 1&#8217;s next greater number is 2; \n    The number 2 can&#8217;t find next greater number. \n    The second 1&#8217;s next greater number needs to search circularly, which is also 2.<\/p>\n\n    <p><strong>Example 2:<\/strong><\/p>\n    <p><strong>Input:<\/strong><\/p>\n        <p>nums = [1,2,3,4,3]<\/p>\n    <p><strong>Output:<\/strong><code> [2,3,4,-1,4]<\/code><\/p>\n\n    <p><strong>Example 2:<\/strong><\/p>\n    <p><strong>Input:<\/strong><\/p>\n        <p>temperatures = [30,40,50,60]<\/p>\n    <p><strong>Output:<\/strong><code> [1,1,1,0]<\/code><\/p>\n\n    <h2>Constraints:<\/h2>\n    <ul>\n        <li><code>1 <= nums.length <= 10<sup>4<\/sup><\/code><\/li>\n        <li><code>-10<sup>9<\/sup> <= temperatures[i] <= 10<\/code><sup>9<\/sup><\/li>\n    <\/ul>\n\n    <h2>Approach:<\/h2>\n    <ul>\n        <li>Initialize:\n\n            <ul>\n                <li><code>n = arr.length<\/code><\/li>\n                <li><code>ans = Array(n).fill(-1)<\/code> \u2192 To store result.<\/li>\n                <li><code>stack = []<\/code> \u2192 To keep track of next greater candidates.<\/li>\n            <\/ul>\n        <\/li>\n        <li><strong>Push last element<\/strong> into stack (start from end).<\/li>\n\n        <li><strong>Traverse from (2n - 2) to 0:<\/strong>\n            <ul>\n                <li>Use i % n to simulate circular behavior.<\/li>\n                <li>While stack is not empty:\n\n                    <ul>\n                        <li>If current element < top of stack \u2192 that is the next greater, store it in <code>ans[i % n]<\/code> and break.<\/li>\n                        <li>Else pop the stack (since it\u2019s not greater).\n                        <\/li>\n                    <\/ul>\n    \n                <\/li>\n            <\/ul>\n\n        <li>Push current element (arr[i % n]) onto the stack.<\/li>\n        <\/li>        \n        <li><strong>Return<\/strong><code>ans<\/code><\/li>\n\n    <h2>Visualisation:<\/h2>\n    <img decoding=\"async\"\n        src=\"https:\/\/namastedev.com\/blog\/wp-content\/uploads\/2025\/07\/Screenshot-2025-07-11-at-2.54.20\u202fPM.png\"\n        alt=\"stack\"\n    \/>\n                <h2>Time Complexity:<\/h2>\n                <li>\n                  <p><strong>Time Complexity = O(n)<\/strong> \n                <\/li> \n                <h2>Space Complexity:<\/h2>\n                <li>\n                  <p><strong>Space Complexity = O(n)<\/strong> \n                <\/p>\n                <\/li>\n\n<h2>Dry Run<\/h2> <div style=\"background: #f9f9f9; border-left: 4px solid var(--primary); padding: 1rem; border-radius: var(--tab-radius); margin: 1rem 0;\"> <p><strong>Input:<\/strong><\/p> <pre style=\"white-space: pre-wrap; background: #fff5ea; padding: 1rem; border-radius: 8px; overflow-x: auto;\"> arr = [73, 74, 75, 71, 69, 72, 76, 73] <\/pre> <p><strong>State Transitions:<\/strong><\/p> <pre style=\"white-space: pre-wrap; background: #fff5ea; padding: 1rem; border-radius: 8px; overflow-x: auto;\"> Initialize: n = 8 ans = [-1, -1, -1, -1, -1, -1, -1, -1] stack = []\nPush last element \u2192 stack = [73]\n\ni = 14 \u2192 arr[6] = 76\n\u2192 stack = [73]\n\u2192 arr[6] > top (76 > 73) \u2192 ans[6] = -1 (no change)\n\u2192 push 76 \u2192 stack = [76]\n\ni = 13 \u2192 arr[5] = 72\n\u2192 top = 76 \u2192 arr[5] < top (72 < 76) \u2192 ans[5] = 76\n\u2192 push 72 \u2192 stack = [76, 72]\n\ni = 12 \u2192 arr[4] = 69\n\u2192 top = 72 \u2192 arr[4] < top (69 < 72) \u2192 ans[4] = 72\n\u2192 push 69 \u2192 stack = [76, 72, 69]\n\ni = 11 \u2192 arr[3] = 71\n\u2192 top = 69 \u2192 arr[3] > top \u2192 pop 69\n\u2192 top = 72 \u2192 arr[3] < top \u2192 ans[3] = 72\n\u2192 push 71 \u2192 stack = [76, 72, 71]\n\ni = 10 \u2192 arr[2] = 75\n\u2192 top = 71 \u2192 arr[2] > top \u2192 pop 71\n\u2192 top = 72 \u2192 arr[2] > top \u2192 pop 72\n\u2192 top = 76 \u2192 arr[2] < top \u2192 ans[2] = 76\n\u2192 push 75 \u2192 stack = [76, 75]\n\ni = 9 \u2192 arr[1] = 74\n\u2192 top = 75 \u2192 arr[1] < top \u2192 ans[1] = 75\n\u2192 push 74 \u2192 stack = [76, 75, 74]\n\ni = 8 \u2192 arr[0] = 73\n\u2192 top = 74 \u2192 arr[0] < top \u2192 ans[0] = 74\n\u2192 push 73 \u2192 stack = [76, 75, 74, 73]\n\ni = 7 \u2192 arr[7] = 73\n\u2192 top = 73 \u2192 arr[7] == top \u2192 pop 73\n\u2192 top = 74 \u2192 arr[7] < top \u2192 ans[7] = 74\n\u2192 push 73 \u2192 stack = [76, 75, 74, 73]\n\ni = 6 \u2192 arr[6] = 76\n\u2192 top = 73 \u2192 arr[6] > top \u2192 pop 73\n\u2192 top = 74 \u2192 arr[6] > top \u2192 pop 74\n\u2192 top = 75 \u2192 arr[6] > top \u2192 pop 75\n\u2192 top = 76 \u2192 arr[6] == top \u2192 pop 76\n\u2192 stack empty \u2192 ans[6] remains = -1\n\u2192 push 76 \u2192 stack = [76]\n\ni = 5 \u2192 arr[5] = 72\n\u2192 top = 76 \u2192 arr[5] < top \u2192 ans[5] already set \u2192 push 72 \u2192 stack = [76, 72]\n\ni = 4 \u2192 arr[4] = 69\n\u2192 top = 72 \u2192 arr[4] < top \u2192 ans[4] already set \u2192 push 69 \u2192 stack = [76, 72, 69]\n\ni = 3 \u2192 arr[3] = 71\n\u2192 top = 69 \u2192 arr[3] > top \u2192 pop 69\n\u2192 top = 72 \u2192 arr[3] < top \u2192 ans[3] already set \u2192 push 71 \u2192 stack = [76, 72, 71]\n\ni = 2 \u2192 arr[2] = 75\n\u2192 top = 71 \u2192 arr[2] > top \u2192 pop 71\n\u2192 top = 72 \u2192 arr[2] > top \u2192 pop 72\n\u2192 top = 76 \u2192 arr[2] < top \u2192 ans[2] already set \u2192 push 75 \u2192 stack = [76, 75]\n\ni = 1 \u2192 arr[1] = 74\n\u2192 top = 75 \u2192 arr[1] < top \u2192 ans[1] already set \u2192 push 74 \u2192 stack = [76, 75, 74]\n\ni = 0 \u2192 arr[0] = 73\n\u2192 top = 74 \u2192 arr[0] < top \u2192 ans[0] already set \u2192 push 73 \u2192 stack = [76, 75, 74, 73]\n<\/pre>\n\n<p><strong>Final Output:<\/strong> <code>[74, 75, 76, 72, 72, 76, -1, 74]<\/code><\/p> <p><strong>Final State:<\/strong> <code>stack = [76, 75, 74, 73]<\/code><\/p> <\/div>\n\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=\"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 nextGreaterElements = function(arr) {\n    let n = arr.length;\n    let stack = [];\n    let ans = Array(n).fill(-1);\n    stack.push(arr[n-1]);\n    for(let i=(2*n)-2; i >= 0; i--){\n        while(stack.length){\n            let top = stack[stack.length-1];\n            if(arr[i % n] < top){\n                ans[i % n] = top;\n                break;\n            } else{\n                stack.pop();\n            }\n        }\n        stack.push(arr[i % n]);\n    }\n    return ans.slice(0, n);\n};\n<\/code>\n<\/pre>\n<\/div>\n\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"py\">\n        <pre><code class=\"language-python\">\ndef nextGreaterElements(arr):\n    n = len(arr)\n    stack = []\n    ans = [-1] * n\n    stack.append(arr[n - 1])\n    for i in range(2 * n - 2, -1, -1):\n        while stack:\n            top = stack[-1]\n            if arr[i % n] < top:\n                ans[i % n] = top\n                break\n            else:\n                stack.pop()\n        stack.append(arr[i % n])\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\">\nimport java.util.Stack;\nclass Solution {\n    public int[] nextGreaterElements(int[] arr) {\n        int n = arr.length;\n        Stack<Integer> stack = new Stack<>();\n        int[] ans = new int[n];\n        for(int i = 0; i < n; i++) ans[i] = -1;\n        stack.push(arr[n - 1]);\n        for(int i = 2 * n - 2; i >= 0; i--) {\n            while(!stack.isEmpty()) {\n                int top = stack.peek();\n                if(arr[i % n] < top) {\n                    ans[i % n] = top;\n                    break;\n                } else {\n                    stack.pop();\n                }\n            }\n            stack.push(arr[i % n]);\n        }\n        return ans;\n    }\n}\n <\/code><\/pre>\n    <\/div>\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;stack&gt;\nusing namespace std;\nvector<int> nextGreaterElements(vector<int>& arr) {\n    int n = arr.size();\n    stack<int> s;\n    vector<int> ans(n, -1);\n    s.push(arr[n - 1]);\n    for(int i = 2 * n - 2; i >= 0; i--) {\n        while(!s.empty()) {\n            int top = s.top();\n            if(arr[i % n] < top) {\n                ans[i % n] = top;\n                break;\n            } else {\n                s.pop();\n            }\n        }\n        s.push(arr[i % n]);\n    }\n    return ans;\n}\n<\/code><\/pre>\n    <\/div>\n\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;stdlib.h&gt;\nvoid nextGreaterElements(int* arr, int n, int* ans) {\n    int* stack = (int*)malloc(n * sizeof(int));\n    int topIndex = -1;\n    for(int i = 0; i < n; i++) ans[i] = -1;\n    stack[++topIndex] = arr[n - 1];\n    for(int i = 2 * n - 2; i >= 0; i--) {\n        while(topIndex >= 0) {\n            int top = stack[topIndex];\n            if(arr[i % n] < top) {\n                ans[i % n] = top;\n                break;\n            } else {\n                topIndex--;\n            }\n        }\n        stack[++topIndex] = arr[i % n];\n    }\n    free(stack);\n}\n<\/code><\/pre>\n    <\/div>\n    <div class=\"wp_blog_code-tab-content\" data-lang=\"cs\">\n        <pre><code class=\"language-csharp\">\nusing System;\nusing System.Collections.Generic;\npublic class Solution {\n    public int[] NextGreaterElements(int[] arr) {\n        int n = arr.Length;\n        Stack<int> stack = new Stack<int>();\n        int[] ans = new int[n];\n        Array.Fill(ans, -1);\n        stack.Push(arr[n - 1]);\n        for(int i = 2 * n - 2; i >= 0; i--) {\n            while(stack.Count > 0) {\n                int top = stack.Peek();\n                if(arr[i % n] < top) {\n                    ans[i % n] = top;\n                    break;\n                } else {\n                    stack.Pop();\n                }\n            }\n            stack.Push(arr[i % n]);\n        }\n        return ans;\n    }\n}\n  <\/code><\/pre>\n    <\/div>\n<\/div>\n<\/div>\n<script>\n    document.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                buttons.forEach((btn) => btn.classList.remove(\"active\"));\n                contents.forEach((content) =>\n                    content.classList.remove(\"active\")\n                );\n                button.classList.add(\"active\");\n                document\n                    .querySelector(\n                        `.wp_blog_code-tab-content[data-lang=\"${lang}\"]`\n                    )\n                    .classList.add(\"active\");\n            });\n        });\n    });\n<\/script>\n","protected":false},"excerpt":{"rendered":"<p>Problem Statement: Given a circular integer array nums (i.e., the next element of nums[nums.length &#8211; 1] is nums[0]), return the next greater number for every element in nums. The next greater number of a number x is the first greater number to its traversing-order next in the array, which means you could search circularly to<\/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":[322,260,176,175,212,211,811,810,174,172,173],"tags":[],"class_list":{"0":"post-7778","1":"post","2":"type-post","3":"status-publish","4":"format-standard","6":"category-algorithms-and-data-structures","7":"category-c-c-plus-plus","8":"category-csharp","9":"category-cplusplus","10":"category-code-optimization","11":"category-data-structures","12":"category-data-structures-and-algorithms","13":"category-dsa","14":"category-java","15":"category-javascript","16":"category-python"},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7778","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=7778"}],"version-history":[{"count":2,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7778\/revisions"}],"predecessor-version":[{"id":7807,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/posts\/7778\/revisions\/7807"}],"wp:attachment":[{"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/media?parent=7778"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/categories?post=7778"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/namastedev.com\/blog\/wp-json\/wp\/v2\/tags?post=7778"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}