1. TUTORIAL 11
CS 137 F18
November 27th

2. Overview a8 Common Mistakes sum_to_zero.c using qsort
multipleChoice.c solutions
a9 Progress
rotate_ll.c
loop_ll.c

3. a8 Common Mistakes a8p1: MultipleChoice.c a8p2: insert_or_merge.c
Very Well Done!
a8p2: insert_or_merge.c
Lots of ways to go about it
Needed to compare the entire array for a merge step
a8p3: sum_to_zero.c
Dealing with the array of size 2
Finding the sum closest to zero in O(n)

4. Recall qsort
In practice, one usually does not create their own sorting algorithm
In C, <stdlib.h> contains qsort:
void qsort ( void * base , size_t n , size_t , size , int (* compare )( const void *a , const void * b ));
base is the beginning of the array
n is the length of the array
size is the size of a byte in the array
*compare is a function pointer to a comparison criteria
How can it be implemented in a8p3?
void sum_closest_to_zero(int a[], int n, int *first, int *second);

5. Solution to multipleChoice.c Question 1
int question_1(int n) { int s = n; for(int i = ; i > 0; i /= 2) printf("Fun!"); return s; }

6. Solution to multipleChoice.c Question 2
int question_2(int n) { int s = 0; for(int i = 0; i < n; i++) for(int j = i/2; j < n; j++) s++; return s; }

7. Solution to multipleChoice.c Question 3
nt question_3(int n) { int s = 0; for(int i = n*n; i>0; i /= n) s++; return s; }

8. Solution to multipleChoice.c Question 4
int q4_q5_helper(int n) { int s = 0; for(int i = 0; i < n; i++) s++; return s; } int question_4(int n){ int t = 0; for(int i = 0; i < n; i++) for(int j = 0; j < q4_q5_helper(n); j++) t++; return t;

9. Solution to multipleChoice.c Question 5
int q4_q5_helper(int n) { int s = 0; for(int i = 0; i < n; i++) s++; return s; } int question_5(int n) { int t = 0; for(int i = 0; i < q4_q5_helper(n); i++) for(int j = 0; j < n; j++) t++; return t;

11. a9 Progress? Questions? Avoid Memory Leaks Boolean Expressions
Care in keeping track of nodes
Care in traversing nodes
Boolean Expressions
For converting a linked list to a double linked list, make sure you are not mutating the linked list
DO NOT use lst->head to traverse the linked list.
Only destroy and remove_item should free any structure on the heap.

12. rotate_ll.c
Given a singly linked list, rotate the linked list counter-clockwise by k nodes.
Can assume k is a non-negative integer.
void rotate(struct ll *lst, int k);
Example Linked List:
1->2->3->4->5->6->7
Rotated Linked List by k = 4:
5->6->7->1->2->3->4

13. loop_ll.c
Given a linked list, check if the linked list has loop or not.
bool detectLoop(struct ll *lst);

14. loop_ll.c continued Given a linked list with a loop, remove the loop.
void removeLoop(struct ll *lst, struct llnode *loop_node);
For more efficient implementations

15. return 0; }