MA335 Homework 3 Solved

All of these functions belong in a file named randomstuff.c.

1.    Write a function int countEven(int* arr, int size) which receives an integer array and its size, and returns the number of even numbers in the array.

2.    Write a function double* maximum(double* a, int size). The input double* a is a pointer to an array of doubles of length size. The return value is a pointer to the largest value in a.

3.    Strings are terminated with the special character ’\0’. Write a function int myStrLen (char* s) which returns the length of a properly terminated string. Write the function without using the function strlen.

4.    Write a function void revString(char* s) which reverses the parameter s. The array s should actually be changed in this example.

1

5.    Write a function void delEven(int* arr,int size) so that it sets all the even entries in arr to -1. It should not return anything, and it should actually modify the array pointed to by arr.

All of these functions belong in a file named primestuff.c

1.    Write a function int isprime(int n)

that returns 1 if the input integer n is prime, and 0 if it is not prime. Your function should indicate that numbers less than 2 are not prime, by definition. You do not need to use anything fancy to determine whether or not n is prime. For reference, % is the mod operator in C.

2.    An integer m is a Mersenne prime if m is prime and there exists an integer p such that m = 2p − 1. For example 3 is a Mersenne prime since 3 is prime and 3 = 22 − 1. However, 2 is not a Mersenne prime, despite being prime.

Write a function int isMersenne(int n)

that returns 1 if n is a Mersenne prime, and 0 otherwise. Your code should call the isprime function written above.

3.    Write a function void prime_info(int* ns,int l, int* num_prime,int* primes, int* num_mersenne

, int* mersennes)

That takes an array of integers, ns, and the length of that array l, and returns in num_prime the number of those integers that are prime, returns in primes the actual array of prime elements of ns, returns in num_mersenne the number of Mersenne primes in ns and returns in mersennes the actual list of Mersenne primes present in ns. Assume that the pointers primes and mersennes already point to arrays that are large enough to hold all the numbers you wish to store in them.

4.    Add a main function to primestuff.c. The final program should take arguments from the command line, and interpret them thusly:

•    If the first argument is exactly --list then all following command line arguments are treated as an array, prime_info is called, and information regarding the result is printed.

•    If the first argument is exactly --range then the following two numbers are treated as a range, for example,

primestuff --range 10 15 should print the prime_info regarding the array [10,11,12,13,14,15].

•    If anything else is the first argument, or if any necessary arguments are missing, then the program simply prints See usage information.

You may find the strlen and/or strcmp and/or strncmp functions useful. In order to use strlen, strcmp, or strncmp you will need #include<string.h>.