Chapter 2.1, Problem 2.11PP

A.

Explanation of Solution

Determining the value of variables “first” and “last” in function “reverse_array”:

From the given question, an array of odd length “cnt = 2k + 1”. Assume k = 0, 1, 2

Case 1:

• When “k = 0”, then “cnt = 2 (0) + 1 = 0 + 1 = 1”.
• Then call the function “reverse_array” with “cnt = 1”.

first	last = cnt - 1	first < = last	inplace_swap(&a[first], &a[last])
first = 0	last = 1 - 1 = 0	0 < = 0	inplace_swap(&a[0], &a[0]) Here the both values are equal so value of middle element “a[0]” is “0”. Therefore, “first = 0” and “last = 0”. That is same as the value of “k”.

Case 2:

• When “k = 1”, then cnt = 2 (1) + 1 = 2 + 1 = 3.
• Then call the function “reverse_array” with “cnt = 3”...

B.

Explanation of Solution

Setting the array element is “0” in the function “inplace_swap”:

• In the “inplace_swap” function, the arguments “x” and “y” point to the same location.
  • Once user compute “*x ^ *y”, then the user get the result of “0”. Because of, value of “a ^ a” is “0” for any “a” in the “inplace_swap” function.
    • It is based on the property of “^”.
  • Calling “inplace_swap” function to the reverse array, the value of middle element becomes “0” for odd array length.

Example:

When the array elements are “1, 2, 3, 4 and 5”, then the reverse array is “5, 4, 0, 2, 1”.

• Call the function “reverse_array” with array “a” 1, 2, 3, 4 and 5 and “cnt = 3”.
• Initially array “a” is

a[0]	a[1]	a[2]	a[3]	a[4]
1	2	3	4	5

• Steps to find the reverse array...

C.

Explanation of Solution

Modification to the code for “reverse_array” function:

• Replace the test condition of “first <=...