CS201 – Spring 2001

Prof. Hartman

Homework #8

Due Friday, April 6th by 4:00 pm

Recommended Self-Review problems: 5.1 – 5.7

Homework to be turned in: (remember that all programs must follow the guidelines from handout #3.)

1. (10 pts) Written:

a) True or False: The declarations int * bar and int bar[] are interchangeable.

b) Write the declaration and initialization for a pointer variable bar that points to a float variable foo.

c) After the following snippet of code what are the values of y and *y assuming that the address of x is 0x40047BC8.
int x = 25;
int *y = &x;

d) Given the snippet of code:

char *message = "Howdy!";

what is output to the screen by the following commands?

i. cout << *(message + 3) << endl;

ii. cout << message + 3 << endl;

iii. cout << (*message) + 3 << endl;

e) Given the snippet of code:

int Grog[ ] = {0, 2, 4, 6, 8};

what is output to the screen by the following commands?

i. cout << *(Grog + 3) << endl;

ii. cout << Grog + 3 << endl;

2. (20 pts) Comparing Strings:
Create a function that will compare two character strings. The function should return (-1) if the first parameter comes before the second in lexicographical ordering (in a dictionary), 0 if they are equal, and 1 if the first parameter comes after the second in a dictionary. Be careful that you do not differentiate between upper and lower case letters. Thus, "aRe" is equal to "are" and "Belmont" comes after "armadillo". You are not allowed to use the string.h functions (if you don't know what these are yet, don't worry about it). You are allowed to use char toupper(char) and char tolower(char) functions from the ctype.h library. You should not restrict the size of the words coming into your function (though you may restrict that in your program when testing your function).

3. (20 pts) Using STL's Sort

It turns out that the Standard Template Library already has a great sorting method: the sort() function. A prototype is shown below.

void sort(int *, int *, bool (* compare)(int, int))

This means that sort takes two pointers to int's and a pointer to a function. To use the sort function, you pass it a pointer to the beginning of your array as the first parameter, a pointer to the first element after your array as the second parameter (note that this second parameter is intentionally out of bounds of your array), and a pointer to a comparison function as the third parameter. The comparison function takes two int's, compares them, and returns a bool: true if the first integer is less than the second, and false otherwise. This function is located in the Standard Template Library; it is declared in the algorithm header file. This header file (like most) puts the functions in the standard namespace.

To use the function, you will need to insert the following lines of code at the beginning of your file.

#include <algorithm>

Now that you know about the STL function sort(), use it in a program that will sort an array of 100 random integers. Create your own comparison functions: one that will cause the array to be sorted in ascending order and another for descending order. Your program should sort the array twice, using the respective comparison functions, and should output the array in both ascending and descending order.