{"id":7235,"date":"2022-08-14T23:15:00","date_gmt":"2022-08-14T17:45:00","guid":{"rendered":"https:\/\/www.codingbroz.com\/?p=7235"},"modified":"2022-07-31T22:06:04","modified_gmt":"2022-07-31T16:36:04","slug":"reverse-nodes-in-k-group-leetcode-solution","status":"publish","type":"post","link":"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/","title":{"rendered":"Reverse Nodes in k-Group &#8211; Leetcode Solution"},"content":{"rendered":"\n<p>In this post, we are going to solve the<strong> 25. Reverse Nodes in k-Group<\/strong> problem of Leetcode. This problem <strong>25. Reverse Nodes in k-Group<\/strong> is a Leetcode <strong>hard <\/strong>level problem. Let&#8217;s see the code, <strong><strong>25. Reverse Nodes in k-Group<\/strong><\/strong> <strong>&#8211; Leetcode Solution<\/strong>.<\/p>\n\n\n\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_65 ez-toc-wrap-left counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<label for=\"ez-toc-cssicon-toggle-item-66362f1a61d57\" class=\"ez-toc-cssicon-toggle-label\"><label class=\"ez-toc-title\">Table of Contents<\/label>\n<span class=\"ez-toc-cssicon\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #0090ff;color:#0090ff\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #0090ff;color:#0090ff\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/label><input type=\"checkbox\"  id=\"ez-toc-cssicon-toggle-item-66362f1a61d57\" checked \/><nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><ul class='ez-toc-list-level-2' ><li class='ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#Problem\" title=\"Problem\">Problem<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#Example_1\" title=\"Example 1 :\">Example 1 :<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#Example_2\" title=\"Example 2 :\">Example 2 :<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#Constraints\" title=\"Constraints\">Constraints<\/a><\/li><\/ul><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-1'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#Reverse_Nodes_in_k-Group_%E2%80%93_Leetcode_Solution\" title=\"Reverse Nodes in k-Group &#8211; Leetcode Solution\">Reverse Nodes in k-Group &#8211; Leetcode Solution<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_Java\" title=\"25. Reverse Nodes in k-Group &#8211; Solution in Java\">25. Reverse Nodes in k-Group &#8211; Solution in Java<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_C\" title=\"25. Reverse Nodes in k-Group &#8211; Solution in C++\">25. Reverse Nodes in k-Group &#8211; Solution in C++<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.codingbroz.com\/reverse-nodes-in-k-group-leetcode-solution\/#25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_Python\" title=\"25. Reverse Nodes in k-Group &#8211; Solution in Python\">25. Reverse Nodes in k-Group &#8211; Solution in Python<\/a><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Problem\"><\/span><strong>Problem<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h2>\n\n\n\n<p>Given the <code>head<\/code> of a linked list, reverse the nodes of the list <code>k<\/code> at a time, and return <em>the modified list.<\/em><\/p>\n\n\n\n<p><code>k<\/code> is a positive integer and is less than or equal to the length of the linked list. If the number of nodes is not a multiple of <code>k<\/code> then left-out nodes, in the end, should remain as it is.<\/p>\n\n\n\n<p>You may not alter the values in the list&#8217;s nodes, only nodes themselves may be changed.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Example_1\"><\/span><strong>Example 1 :<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code has-ast-global-color-5-color has-ast-global-color-8-background-color has-text-color has-background\"><code>\nInput: head = &#91;1,2,3,4,5], k = 2\r\nOutput: &#91;2,1,4,3,5]\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Example_2\"><\/span><strong>Example 2 :<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"wp-block-code has-ast-global-color-5-color has-ast-global-color-8-background-color has-text-color has-background\"><code>\nInput: head = &#91;1,2,3,4,5], k = 3\r\nOutput: &#91;3,2,1,4,5]\n<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Constraints\"><\/span><strong>Constraints<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<ul><li>The number of nodes in the list is <code>n<\/code>.<\/li><li><code>1 &lt;= k &lt;= n &lt;= 5000<\/code><\/li><li><code>0 &lt;= Node.val &lt;= 1000<\/code><\/li><\/ul>\n\n\n\n<p>Now, let&#8217;s see the code of <strong>25. Reverse Nodes in k-Group<\/strong> &#8211; Leetcode Solution.<\/p>\n\n\n\n<h1 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"Reverse_Nodes_in_k-Group_%E2%80%93_Leetcode_Solution\"><\/span><strong><strong><strong><strong><strong><strong><strong>Reverse Nodes in k-Group &#8211; Leetcode Solution<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><span class=\"ez-toc-section-end\"><\/span><\/h1>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_Java\"><\/span><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong>25. Reverse Nodes in k-Group<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong> &#8211; Solution in Java<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"java\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/**\n * Definition for singly-linked list.\n * public class ListNode {\n *     int val;\n *     ListNode next;\n *     ListNode() {}\n *     ListNode(int val) { this.val = val; }\n *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }\n * }\n *\/\nclass Solution {\n    \n    public int length(ListNode head){\n        ListNode curr = head;\n        int len = 0;\n        while(curr != null){\n            curr = curr.next;\n            len++;\n        }\n        return len;\n    }\n    \n    private ListNode th = null;\n    private ListNode tt = null;\n    \n    private void addFirstNode(ListNode node){\n        if(th == null){\n            th = node;\n            tt = node;\n        }\n        else{\n            node.next = th;\n            th = node;\n        }\n    }\n    \n    public ListNode reverseKGroup(ListNode head, int k) {\n        \n        if(head == null || head.next == null || k == 0) return head;\n        \n        ListNode oh = null;\n        ListNode ot = null;\n        \n        ListNode curr = head;\n        int len = length(curr);\n        \n        while(len >= k){\n            int tempK = k;\n           \n            \n            while(tempK-- > 0){\n                ListNode forw = curr.next;\n                curr.next = null;\n                addFirstNode(curr);\n               curr = forw;\n            }\n            \n            if(oh == null){\n                oh = th;\n                ot = tt;\n            }else{\n                ot.next = th;\n                ot = tt;\n            }\n            \n            th = null;\n            tt = null;\n            len -= k;\n        }\n        \n        ot.next = curr;\n        return oh;\n    }\n}<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_C\"><\/span><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong>25. Reverse Nodes in k-Group<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong> &#8211; Solution in <\/strong>C++<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"cpp\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\">\/**\n * Definition for singly-linked list.\n * struct ListNode {\n *     int val;\n *     ListNode *next;\n *     ListNode() : val(0), next(nullptr) {}\n *     ListNode(int x) : val(x), next(nullptr) {}\n *     ListNode(int x, ListNode *next) : val(x), next(next) {}\n * };\n *\/\nclass Solution {\npublic:\n    ListNode* reverseKGroup(ListNode* head, int k) {\n        if(head==NULL||k==1) return head;\n        ListNode *dummy=new ListNode();\n        dummy->next=head;\n        ListNode *cur=dummy,*nex=dummy,*pre=dummy;\n        int count=0;\n        while(cur->next!=NULL){\n            cur=cur->next;\n            count++;\n        }\n        while(count>=k){\n            cur=pre->next;\n            nex=cur->next;\n            for(int i=1;i&lt;k;i++){\n                cur->next=nex->next;\n                nex->next=pre->next;\n                pre->next=nex;\n                nex=cur->next;\n            }\n            pre=cur;\n            count-=k;\n        }\n        return dummy->next;\n    }\n};<\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><span class=\"ez-toc-section\" id=\"25_Reverse_Nodes_in_k-Group_%E2%80%93_Solution_in_Python\"><\/span><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong><strong>25. Reverse Nodes in k-Group<\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong><\/strong> <strong><strong><strong>&#8211; Solution in <\/strong><\/strong>Python<\/strong><span class=\"ez-toc-section-end\"><\/span><\/h3>\n\n\n\n<pre class=\"EnlighterJSRAW\" data-enlighter-language=\"python\" data-enlighter-theme=\"\" data-enlighter-highlight=\"\" data-enlighter-linenumbers=\"\" data-enlighter-lineoffset=\"\" data-enlighter-title=\"\" data-enlighter-group=\"\"># Definition for singly-linked list.\n# class ListNode:\n#     def __init__(self, val=0, next=None):\n#         self.val = val\n#         self.next = next\nclass Solution:\n    def reverseKGroup(self, head: Optional[ListNode], k: int) -> Optional[ListNode]:\n        if not head:\n            return head\n        a = b = head\n        for _ in range(k):\n            if not b:\n                return a\n            b = b.next\n            \n        new_head = self.reverse(a, b)\n        a.next = self.reverseKGroup(b, k)\n        return new_head\n    \n    def reverse(self, a, b):\n        pre = None\n        cur = a\n        nxt = a\n        while cur != b:\n            nxt = cur.next\n            cur.next = pre\n            pre = cur\n            cur = nxt\n            \n        return pre\n        <\/pre>\n\n\n\n<p><strong>Note:<\/strong> This problem <strong><a href=\"https:\/\/leetcode.com\/problems\/reverse-nodes-in-k-group\/\" target=\"_blank\" rel=\"noreferrer noopener\">25. Reverse Nodes in k-Group<\/a><\/strong> is generated by <strong><a href=\"https:\/\/leetcode.com\/\" target=\"_blank\" rel=\"noreferrer noopener\">Leetcode<\/a> <\/strong>but the solution is provided by <strong><a href=\"https:\/\/www.codingbroz.com\/\">CodingBroz<\/a><\/strong>. This tutorial is only for <strong>Educational<\/strong> and <strong>Learning<\/strong> purpose.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>In this post, we are going to solve the 25. Reverse Nodes in k-Group problem of Leetcode. This problem 25. Reverse Nodes in k-Group is a Leetcode hard level problem. Let&#8217;s see the code, 25. Reverse Nodes in k-Group &#8211; Leetcode Solution.<\/p>\n","protected":false},"author":3,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[688],"tags":[130,689,764],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","jetpack-related-posts":[],"_links":{"self":[{"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/posts\/7235"}],"collection":[{"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/users\/3"}],"replies":[{"embeddable":true,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/comments?post=7235"}],"version-history":[{"count":2,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/posts\/7235\/revisions"}],"predecessor-version":[{"id":7237,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/posts\/7235\/revisions\/7237"}],"wp:attachment":[{"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/media?parent=7235"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/categories?post=7235"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.codingbroz.com\/wp-json\/wp\/v2\/tags?post=7235"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}