1. 5.13 Recursion Recursive functions Functions that call themselves
Can only solve a base case
Divide a problem up into
What it can do
What it cannot do
What it cannot do resembles original problem
The function launches a new copy of itself (recursion step) to solve what it cannot do
Eventually base case gets solved
Gets plugged in, works its way up and solves whole problem

2. 5.13 Recursion Example: factorials Notice that
5! = 5 * 4 * 3 * 2 * 1
Notice that
5! = 5 * 4!
4! = 4 * 3! ...
Can compute factorials recursively
Solve base case (1! = 0! = 1) then plug in
2! = 2 * 1! = 2 * 1 = 2;
3! = 3 * 2! = 3 * 2 = 6;

3. 5.13 Recursion

4. fig05_14.c (Part 1 of 2)

5. fig05_14.c (Part 2 of 2)
1! = 1
2! = 2
3! = 6
4! = 24
5! = 120
6! = 720
7! = 5040
8! = 40320
9! =
10! =

6. 5.14 Example Using Recursion: The Fibonacci Series
Each number is the sum of the previous two
Can be solved recursively:
fib( n ) = fib( n - 1 ) + fib( n – 2 )
Code for the fibonacci function
long fibonacci( long n ) {
if (n == 0 || n == 1) // base case
return n;
else
return fibonacci( n - 1) fibonacci( n – 2 ); }

7. 5.14 Example Using Recursion: The Fibonacci Series
Set of recursive calls to function fibonacci
f( 3 )
f( 1 )
f( 2 )
f( 0 )
return 1
return 0
return +

8. fig05_15.c (Part 1 of 2)

9. fig05_15.c (Part 2 of 2) Program Output
Enter an integer: 0
Fibonacci( 0 ) = 0
Enter an integer: 1
Fibonacci( 1 ) = 1
Enter an integer: 2
Fibonacci( 2 ) = 1
Enter an integer: 3
Fibonacci( 3 ) = 2
Enter an integer: 4
Fibonacci( 4 ) = 3

10. Program Output (continued)
Enter an integer: 5
Fibonacci( 5 ) = 5
Enter an integer: 6
Fibonacci( 6 ) = 8
Enter an integer: 10
Fibonacci( 10 ) = 55
Enter an integer: 20
Fibonacci( 20 ) = 6765
Enter an integer: 30
Fibonacci( 30 ) =
Enter an integer: 35
Fibonacci( 35 ) =
Program Output (continued)

11. 5.14 Example Using Recursion: The Fibonacci Series

12. 5.15 Recursion vs. Iteration
Repetition
Iteration: explicit loop
Recursion: repeated function calls
Termination
Iteration: loop condition fails
Recursion: base case recognized
Both can have infinite loops
Balance
Choice between performance (iteration) and good software engineering (recursion)

13. 14.4 Using Command-Line Arguments
Pass arguments to main on DOS or UNIX
Define main as
int main( int argc, char *argv[] )
int argc
Number of arguments passed
char *argv[]
Array of strings
Has names of arguments in order
argv[ 0 ] is first argument
Example: $ mycopy input output
argc: 3
argv[ 0 ]: “mycopy"
argv[ 1 ]: "input"
argv[ 2 ]: "output"

14. Notice argc and argv[] in main
fig14_03.c (Part 1 of 2)
argv[1] is the second argument, and is being read.
argv[2] is the third argument, and is being written to.
Loop until End Of File. fgetc a character from inFilePtr and fputc it into outFilePtr.

15. fig14_03.c (Part 2 of 2)

16. 12.1 Introduction Dynamic data structures Linked lists Stacks Queues
Data structures that grow and shrink during execution
Linked lists
Allow insertions and removals anywhere
Stacks
Allow insertions and removals only at top of stack
Queues
Allow insertions at the back and removals from the front
Binary trees
High-speed searching and sorting of data and efficient elimination of duplicate data items

17. 12.2 Self-Referential Structures
Structure that contains a pointer to a structure of the same type
Can be linked together to form useful data structures such as lists, queues, stacks and trees
Terminated with a NULL pointer (0)
struct node { int data; struct node *nextPtr; }
nextPtr
Points to an object of type node
Referred to as a link
Ties one node to another node

18. 12.3 Dynamic Memory Allocation
Figure 12.1 Two self-referential structures linked together 10 15

19. 12.3 Dynamic Memory Allocation
Obtain and release memory during execution
malloc
Takes number of bytes to allocate
Use sizeof to determine the size of an object
Returns pointer of type void *
A void * pointer may be assigned to any pointer
If no memory available, returns NULL
Example
newPtr = malloc( sizeof( struct node ) );
free
Deallocates memory allocated by malloc
Takes a pointer as an argument
free ( newPtr );

20. 12.4 Linked Lists Linked list
Linear collection of self-referential class objects, called nodes
Connected by pointer links
Accessed via a pointer to the first node of the list
Subsequent nodes are accessed via the link-pointer member of the current node
Link pointer in the last node is set to NULL to mark the list’s end
Use a linked list instead of an array when
You have an unpredictable number of data elements
Your list needs to be sorted quickly

21. Linked Lists

22. fig12_03.c (Part 1 of 8)

23. fig12_03.c (Part 2 of 8)

24. fig12_03.c (Part 3 of 8)

25. fig12_03.c (Part 4 of 8)

26. fig12_03.c (Part 5 of 8)

27. fig12_03.c (Part 6 of 8)

28. fig12_03.c (Part 7 of 8)

29. fig12_03.c (Part 8 of 8)

30. Program Output (Part 1 of 3)
Enter your choice:
1 to insert an element into the list.
2 to delete an element from the list.
3 to end.
? 1
Enter a character: B
The list is:
B --> NULL
Enter a character: A
A --> B --> NULL
Enter a character: C
A --> B --> C --> NULL
? 2
Enter character to be deleted: D
D not found.
Enter character to be deleted: B
B deleted.
A --> C --> NULL
Program Output (Part 1 of 3)

31. Program Output (Part 2 of 3)
? 2
Enter character to be deleted: C
C deleted.
The list is:
A --> NULL
Enter character to be deleted: A
A deleted.
List is empty.
? 4
Invalid choice.
Enter your choice:
1 to insert an element into the list.
2 to delete an element from the list.
3 to end.
? 3
End of run.
Program Output (Part 2 of 3)

32. Program Output (Part 3 of 3)
? 4
Invalid choice.
Enter your choice:
1 to insert an element into the list.
2 to delete an element from the list.
3 to end.
? 3
End of run.
Program Output (Part 3 of 3)

33. Linked Lists