CS-362: Data Structures Week 6 Part 2

1. CS-362: Data StructuresWeek 6Part 2 Dr. Jesús Borrego

2. Topics • Dynamic Data • Pointers • Address • Pointers to different data types • Sample programs

3. Pointer Data Type/Pointer Variables 325 The type is integer The Name of the integer is A The address is 10280 The value stored in A is 325 int A = 325; 10280 A

4. More Pointers

5. Running the program

6. Running the program

7. PointerAndAddress

8. Declaring Pointer Variables • Syntax: • Examples: int *p; char *ch; • These statements are equivalent: int *p; int* p; int * p;

9. Pointer Intro Program (I)

10. Pointer Intro Program (II)

11. Running the program

12. Pointer Intro Program (I)

13. Pointer Intro Program (II)

14. Pointer Intro Program (II)

15. MoreStruct

16. Running the program

17. MoreBeatles (I)

18. MoreBeatles (II)

19. MoreBeatles (III)

20. Running the program

21. PointerSwap

22. Running the Program

23. What happened? The swap did not work? The before and after are the same Need to make sure we get the values back to the calling program It is calling by Value How do we fix it?

24. Address of Operator (&) The ampersand, &, is called the address of operator The address of operator is a unary operator that returns the address of its operand

25. PointerSwap2

26. PointerSwap3

27. Running the program (I)

28. Running the program (II)

29. stores 25 into the first memory location stores 35 into the second memory location Dynamic Arrays • Dynamic array: array created during the execution of a program • Example: int *p; p = new int[10]; *p = 25; p++; //to point to next array component *p = 35;

30. Dynamic Arrays (cont'd.) • C++ allows us to use array notation to access these memory locations • The statements: p[0] = 25; p[1] = 35; store 25 and 35 into the first and second array components, respectively

31. Dynamic Arrays (cont'd.)

32. Dynamic Arrays (cont'd.)

33. Dynamic Arrays (cont'd.) • The value of list (1000) is constant • Cannot be altered during program execution • The increment and decrement operations cannot be applied to list • If p is a pointer variable of type int, then: p = list; copies the value of list, the base address of the array, into p • We can perform ++ and -- operations on p • An array name is a constant pointer

34. Dynamic Arrays (cont'd.)

35. Functions and Pointers • A pointer variable can be passed as a parameter either by value or by reference • To make a pointer a reference parameter in a function heading, use &: void pointerParameters(int* &p, double *q) { . . . }

36. Pointers and Function Return Values • A function can return a value of type pointer: int* testExp(...) { . . . }

37. declares board to be an array of four pointers wherein each pointer is of type int creates the rows of board declares board to be a pointer to a pointer Dynamic Two-Dimensional Arrays • You can create dynamic multidimensional arrays • Examples:

38. PointerArray

39. PointerArray (Cont’d)

40. Running the program

41. PrintArray2D

42. PrintArray2D (Cont’d)

43. PrintArray (Cont’d)

44. Running the Program

45. Resources • Can search the internet for tutorials on pointers • On YouTube: • http://www.youtube.com/watch?v=eFWCQexfaeg • From Google, search for • “C++ pointer tutorial“