You are given a C file hw04q1.c which contains a partially completed program. Follow the instructions contained in comments and complete the required functions. You will be rewriting most functions from HW03 (initializeStrings, printStrings, reverseStrings, encryptStrings, decryptStrings) using only pointer operations instead of using array operations. In this homework, the arrays in all functions need to be accessed with pointer, not as array. It means you cannot use array indexing like s[0][0]. You will be using a character pointer. You may use only the strlen( ) function from string.h library. You can find out more about these functions by reading through the instructions in the hw04q1.c file. Example output is given below.

#include #include

#pragma warning(disable : 4996) // compiler directive for Visual Studio only

// Read before you start: // You are given a partially complete program. Complete the functions in order for this program to work successfully. // All instructions are given above the required functions, please read them and follow them carefully. // You shoud not modify the function return types or parameters. // You can assume that all inputs are valid. Ex: If prompted for an integer, the user will input an integer. // You can use only the strlen() of strings.h library to check string length. Do not use any other string functions // because you are supposed to use pointers for this homework. // **** DO NOT use arrays to store or to index the characters in the string ****

// Global Macro Values. They are used to define the size of 2D array of characters #define NUM_STRINGS 4 #define STRING_LENGTH 50

// Forward Declarations void initializeStrings(char[NUM_STRINGS][STRING_LENGTH]); void printStrings(char[NUM_STRINGS][STRING_LENGTH]); void encryptStrings(char[NUM_STRINGS][STRING_LENGTH], int); void decryptStrings(char[NUM_STRINGS][STRING_LENGTH], int); void reverseStrings(char strings[NUM_STRINGS][STRING_LENGTH]); char* reverseOneString(char s[STRING_LENGTH]); int isPalindrome(char s[STRING_LENGTH]);

// Problem 1: initializeStrings (5 points) // Use pointer p to traverse the 2D array of characters variable 'strings' (input from user in main() ) and set all characters in each // array to a null terminator so that there is a 4 row and 50 column 2D array full of null terminators. // The null terminator '\0' is used to denote the end of a string. void initializeStrings(char strings[NUM_STRINGS][STRING_LENGTH]) { char *ptr = &strings[0][0]; // enter code here

}

// Problem 2: printStrings (5 points) // Use pointer p to traverse the 2D character array "strings" and print each string. // See the example outputs provided in the word document. Each string should be printed on a new line. void printStrings(char strings[NUM_STRINGS][STRING_LENGTH]) { char *ptr = &strings[0][0]; // enter code here

}

// Problem 3: reverseOneString (15 points) // Reverse the string s by using pointer. // Use pointer p and 'temp' char to swap 1st char with last, then 2nd char with (last-1) and so on.. // Finally return pointer p which points to start of the reversed string. // You may declare and use more pointers if needed. // Hint: You might want to check if your logic works with even as well as odd length string. // You can write test code to print out the reversed string to check if your function works. (Don't include it in final submission) char* reverseOneString(char s[STRING_LENGTH]) { char temp; // not necessary to use this variable char *p = &s[0]; // pointer to start of string // enter code here

return p; }

// Problem 4: reverseStrings (5 points) // Reverse all the strings in 'strings[][]' // For each string in 'strings', use the reverseOneString() to reverse it. // You may declare and use more pointers if needed. void reverseStrings(char strings[NUM_STRINGS][STRING_LENGTH]) { char *ptr = &strings[0][0]; // enter code here

}

// Problem 5: encryptStrings (5 points) // Use pointer ptr to traverse the 2D character array 'strings' and encrypt each string in 2 step as follows- // 1) Reverse the strings. Hint: Use 'reverseStrings()' for this step. // 2) Shift the characters forward by the integer value of 'key'. // If the string is "hello" and key = 2, reversing will get you "olleh" and adding key to it will result in "qnnfj". // Once the value of 'key' gets larger, you will extend past alphabetical characters and reach non-alphabetical characters. Thats ok. // NOTE: DO NOT encrypt the null terminator character. Use the null terminator to find the end string. // If you could not implement reverseStrings(), skip using it in this function. You will receive partial credit. void encryptStrings(char strings[NUM_STRINGS][STRING_LENGTH], int key) { char *p = &strings[0][0]; // enter code here

} // Problem 6: decryptStrings (5 points) // HINT: This should be very similiar to the encryption function defined above in encryptStrings(). // Use pointer p to traverse the 2D character array 'strings' and decrypt each string in 2 step as follows- // 1) Shift the characters backward by the integer value of 'key'. // 2) Reverse the strings. Hint: Use 'reverseStrings()' for this step. // NOTE: DO NOT decrypt the null characters. // If you could not implement reverseStrings(), skip using it in this function. You will receive partial credit. void decryptStrings(char strings[NUM_STRINGS][STRING_LENGTH], int key) { char *ptr = &strings[0][0]; // enter code here

}

// Problem 7: isPalindrome (10 points) // Return 1 if string s is palindrome. // Parse through the string to check if 1st char==last char, 2nd char == (last-1) char, and so on.. // Return 1 if string is palindrome. Return 0 if string is not palindrome. // A palindrome is a sequence of characters which when reversed, is the same sequence of characters. // Palindrome string examples: rotor, noon, madam // Note: you may use reverseOneString() here but it is not necessary to use it. int isPalindrome(char s[STRING_LENGTH]) { char *p = s; int palindrome = 1; // edit if needed // enter code here

return palindrome; }

// You should study and understand how main() works. // *** DO NOT modify it in any way *** int main() { char strings[NUM_STRINGS][STRING_LENGTH]; // will store four strings each with a max length of 34 int i, key; char input[STRING_LENGTH]; printf("CSE240 HW4: Pointers "); initializeStrings(strings); for (i = 0; i

getchar(); // flush out newline ' ' char

printf(" Checking for palindrome. Enter a string: "); // prompt for string fgets(input, sizeof(input), stdin); // store input string input[strlen(input) - 1] = '\0'; // convert trailing ' ' char to '\0' (null terminator)

if (isPalindrome(input)) printf("The string is a palindrome"); else printf("The string is not a palindrome");

getchar(); // keep VS console open return 0; }

Enter a string: Arizona State University Enter a string: Tempe Enter a string: Sun Devils Enter a string: CSE240 Enter a key value for encryption: 3 Encrypted Strings: wlvuhylqx#hwdwV#dar}lud hsphw volyhe#qxV 375HVE Decrypted Strings: Arizona State University Tempe Sun Devils CSE240 Checking for palindrome. Enter a string: racecar The string is a palindrome, Enter a string: Arizona State University Enter a string: Tempe Enter a string: Sun Devils Enter a string: CSE240 Enter a key value for encryption: 3 Encrypted Strings: wlvuhylqx#hwdwV#dar}lud hsphw volyhe#qxV 375HVE Decrypted Strings: Arizona State University Tempe Sun Devils CSE240 Checking for palindrome. Enter a string: racecar The string is a palindrome