Exercise 1.19 - reverse a string

Question

Write a function reverse(s) that reverses the character string s. Use it to write a program that reverses its input a line at a time.

Solution

Explanation

A string in C is a character array which ends in 0. getline is a function in our program, which reads one character at a time using getchar and stores it in a character array called s[] and it returns the length of the array. We call the reverse function on our line. In the reverse function, we calculate the length of the line minus 0 and n if that is present. This determines the ultimate printable characters in the line from where we have to reverse.

We have to two incides, j=0 and i the last printable character and run through the program of swapping those characters till j < i. This reverses the contents of our string.

The crux of the program is this:

    j = 0;

while(j < i)
{
  temp = rline[j];
  rline[j] = rline[i];
  rline[i] = temp;
  --i;
  ++j;
}