Data Structure Linked List: Reverse a Linked List in groups of given size

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 #include <map>
 9 #include <set>
10 using namespace std;
11 
12 struct node {
13     int data;
14     node *next;
15     node() : data(0), next(NULL) { }
16     node(int d) : data(d), next(NULL) { }
17 };
18 
19 void push(node* &head, int k) {
20     node *new_node = new node(k);
21     new_node->next = head;
22     head = new_node;
23 }
24 
25 node* reverselist(node *&head, int k) {
26     node *cur = head;
27     node *pre = NULL;
28     node *next;
29     int c = 0;
30     while (cur && c < k) {
31         next = cur->next;
32         cur->next = pre;
33         pre = cur;
34         cur = next;
35         c++;
36     }
37     if (next) head->next = reverselist(next, k);
38     return pre;
39 }
40 
41 void print(node *head) {
42     while (head) {
43         cout << head->data << " ";
44         head = head->next;
45     }
46 }
47 
48 int main() {
49     node *head = NULL;
50     push(head, 8);
51     push(head, 7);
52     push(head, 6);
53     push(head, 5);
54     push(head, 4);
55     push(head, 3);
56     push(head, 2);
57     push(head, 1);
58     head = reverselist(head, 3);
59     print(head);
60     return 0;
61 }