Question

write C code that uses pointers, arrays, and C strings.

3. Write a function called pow_xy. The function should be passed 2 parameters, as illustrated in the prototype below.

int pow_xy(int *xptr, int y);

Assuming that xptr contains the address of variable x, pow_xy should compute x to the y power, and store the result as the new value of x. The function should also return the result. Do not use the built-in C function pow.

For the remaining problems, use array syntax if a parameter in a function’s prototype is specified as an array (using [ ]), and pointer syntax if a parameter is specified as a pointer (no [ ] allowed).

4. Write a function called init_array. It is passed 3 parameters, as specified in the prototype below:

int init_array(int array[], int len, int start_value);

The ith item in array should be initialized to the value start_value * i. Also, the function should return the sum of the values in array after initialization.

5. Write a function called reverse_numbers. Here is its prototype:

void reverse_numbers(int *arrayptr, int len);

The function is passed a pointer to the beginning of an array of ints (and of course the length of the array as a 2nd parameter). The function should reverse the ordering of the numbers in the array.

For the remaining problems, you may not use any functions in .<string.h>

6. Write a function called streql. Here is its prototype:

int streql(char *strptr1, char *strptr2);

It is passed two parameters, both of which are pointers to C strings. It returns a non-zero integer if the strings consist of the same sequence of characters (with a ‘\0’ at the end), or 0 otherwise.

Here are some examples of how your code should work:

streql("bin", "bag"); // returns 0

streql("computer", "game"); // returns 0

streql("computer", "computer"); // returns a non-zero

int streql("are", "area"); // returns 0

7. Write a function called strcmp373. Here is its prototype:

int strcmp373(char str1[], char str2[]);

It is passed two parameters, both of which are C strings. It returns 0 if the strings are the same alphabetically, or a negative integer if str1 is alphabetically before str2, or a positive integer otherwise.

Here are some examples of how your code should work:

strcmp373("bin", "bag"); // returns s positive int

strcmp373("computer", "game"); // returns a negative int

strcmp373("computer", "computer"); // returns 0

strcmp373("are", "area"); // returns a negative int

8. Write a function called strcat373. The function is passed two parameters, both of which are pointers to C strings. Here is its prototype:

char *strcat373(char *destptr, char *srcptr);

The function should modify the first string (array) so that contains the concatenation of the two strings. For example:

int main() {

char str1[9] = "comp";

char str2[ ] = "uter";

printf("str1 contains %s\n, str1); // prints computer

Note that strcat373 is guaranteed to work properly only if str1's length is big enough to contain the concatenation of the two strings. In this case, "computer" takes up 9 bytes, and since str1 is 9 bytes, the function should run properly since the array is just long enough to contain “computer” (plus ‘\0’). On the other hand,

:

char str1[] = "comp"; // only 5 bytes

char str2[] = "uter";

strcat373(str1, str2); // takes up 9 bytes and

// therefore overflows str1

Upon execution, a runtime error may occur, or (even worse) no runtime error will occur, but some other variable(s) in your program may be overwritten.

Answer 1

***Please upvote if you liked the answer***

Screenshot of the functions and a main function for demonstration:-

#include <stdio.h> int pow_xy (int *xptr, int y) int i=0; //To store the result as the new value of x int val = 1; for (i = 0;i<y;i++) val - val * *xptr; //To Return the result return val; init_array(int array[], int len, int start value) int i=0, sum = 0; Ο Ε © ω for (i = 0;i<len; i++) { //The im item in array should be initialized to the value start value * i array[i] = start_value * i; sum = sum + (start_value # i); Β η ση - //Returning the sum of the values in array after initialization return sum; ο ιο Ο void reverse_numbers (int *arrayptr, int len) Ε Ν Ω int i, j, temp; for (i = len - 1,j = 0;i>=0; i--) Ν Ι Ο 1/Reversing operation if (i != j) Ο Ο Ο Ο temp = arrayptri); arrayptr[i] = arrayptr[i]; arrayptr[i] = temp; Ε Ν Ω //If the array reaches or crosses the midpoint, stop iteration else if (j >= i) Ν Ι Ο break; Ο Ο Ο j++; Ο Ε ω int streql (char *strptri, char *strptr2) Β η int result; Οι while (*strptri != '\0' || *strptr2 != '\0') - Ο Ο if(*strptrl++ == *strptr2++) Ο Ε result = 1; Ν ω // While encountering non-matching characters else Β η Οι result = 0; break; - Ο Ο Ο Ε Ν //If the strings are of unequal size if (*strptr2 != '\0') result = 0; ω Β Ι return result; Ο Ο Ο int strcmp 373 (char strill, char str2(1) Ο Ο int i = 0; Ε Ν int result; ω Β //Looping till one of the strings ends while (str1[i] != '\0' 11 str2[i] != '\0') η ση Ο Ο //If any character in the first string is found alphabetically after //the corresponding character in the second string if (str1[i] > str2[i]) Ο Ε result = 1; break; Ν Β Ο Ο //If any character in the first string is found alphabetically before //the corresponding character in the second string else if (str1[i] < str2[i]) Ο Ο Ο result = -1; break; Ο Ε Ν Ο //If any character in the first string is found alphabetically same as //the corresponding character in the second string else result = 0; Ο Ο Ο Ο Ο i++; Ο Ο return result; Ο ω Β char *strcat 373 (char *destptr, char *srcptr) π Οι // Moving to the end of the destination string while (*destptr != '\0') - ο ο *destptr++; ο // Looping till the end of the second string is reached while (*srcptr != '\0') ω Δ //Appending each character from the second string to the first string destptr++ = *srcptr++; η Οι - Ο Ο Ο void main() { int x - 2,= 3,i; int arr[5] Ο ω char str1[9] = "comp"; char str2[] = "uter"; Β Η Ο Ο /Testing pow w printf("%d\n", pow_xy(x, y)); /Testing in array printf("%d\n", init_array(arr,5,1)); Ο Ο Ο reverse_numbers (Garr[0],5); Ο ω //Testing if the array is reversed for(i = 0;i<5;i++) Β η Οι printf("%d", arr[i]); - ο ο //Testing the www printf("\ntd\n", streql ("bin", "bag")); printf("%d\n", streql ("computer", "computer")); printf("%d\n", streql ("are", "area")); ο Ε ω Α η // Testing the s un 73 printf("\ntd\n", strcmp 373 ("bin", "bag")); printf("%d\n", strcmp 373 ("computer", "game")); printf("%d\n", strcmp 373 ("computer", "computer")); printf("%d\n", strcmp373 ("are", "area")); ση - ο ο /Testing the www .373 strcat 373 (&stri[0],str2[0]); ο Ο printf("tal contains $3", stri); ω Α η ση 167 168

Screenshot of the output:-

5 4 3 2 1 11 1 9 -1 stri contains computer Process returned 22 (0x16) Press any key to continue. execution time : 0.098 s

C code to copy:-

#include <stdio.h>

int pow_xy(int *xptr,int y)
{
int i=0;

//To store the result as the new value of x
int val = 1;
for(i = 0;i<y;i++)
{
val = val * *xptr;
}
//To Return the result
return val;
}

int init_array(int array[], int len, int start_value)
{
int i=0,sum = 0;

for(i = 0;i<len;i++)
{
//The ith item in array should be initialized to the value start_value * i
array[i] = start_value * i;
sum = sum + (start_value * i);
}
//Returning the sum of the values in array after initialization
return sum;
}

void reverse_numbers(int *arrayptr, int len)
{
int i,j,temp;
for(i = len - 1,j = 0;i>=0;i--)
{
//Reversing operation
if (i != j && i > j)
{
temp = arrayptr[i];
arrayptr[i] = arrayptr[j];
arrayptr[j] = temp;
}
//If the array reaches or crosses the midpoint,stop iteration
else if(j >= i)
{
break;
}

j++;
}
}

int streql(char *strptr1, char *strptr2)
{
int result;

while(*strptr1 != '\0' || *strptr2 != '\0')
{
if(*strptr1++ == *strptr2++)
{
result = 1;
}
//While encountering non-matching characters
else
{
result = 0;
break;
}
}

//If the strings are of unequal size
if(*strptr2 != '\0')
result = 0;

return result;
}

int strcmp373(char str1[], char str2[])
{
int i = 0;

int result;

//Looping till one of the strings ends
while(str1[i] != '\0' || str2[i] != '\0')
{
//If any character in the first string is found alphabetically after
//the corresponding character in the second string
if(str1[i] > str2[i])
{
result = 1;
break;
}

//If any character in the first string is found alphabetically before
//the corresponding character in the second string
else if(str1[i] < str2[i])
{
result = -1;
break;
}
//If any character in the first string is found alphabetically same as
//the corresponding character in the second string
else
result = 0;

i++;

}
return result;
}

char *strcat373(char *destptr, char *srcptr)
{
//Moving to the end of the destination string
while(*destptr != '\0')
{
*destptr++;
}
//Looping till the end of the second string is reached
while(*srcptr != '\0')
{
//Appending each character from the second string to the first string
*destptr++ = *srcptr++;
}
}

//Main method for testing purposes
void main(){
int x = 2,y = 3,i;
int arr[6];

char str1[9] = "comp";
char str2[] = "uter";

//Testing pow_xy
printf("%d\n",pow_xy(&x,y));
//Testing init_array
printf("%d\n",init_array(arr,6,1));

reverse_numbers(&arr[0],6);

//Testing if the array is reversed
for(i = 0;i<6;i++)
{
printf("%d ",arr[i]);
}
//Testing the streql
printf("\n%d\n",streql("bin", "bag"));
printf("%d\n",streql("computer", "computer"));
printf("%d\n",streql("are", "area"));

//Testing the strcmp373
printf("\n%d\n",strcmp373("bin", "bag"));
printf("%d\n",strcmp373("computer", "game"));
printf("%d\n",strcmp373("computer", "computer"));
printf("%d\n",strcmp373("are", "area"));

//Testing the strcat373
strcat373(&str1[0],&str2[0]);

printf("str1 contains %s",str1);
}