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

http://www.geeksforgeeks.org/reverse-a-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 }