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#include <stdio.h>
/* The C Programming Language: 2nd Edition
*
* Exercise 1-19: 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.
*
* Answer: This is really just as simple as using get_line() and reverse() in
* tandem. I guess the point of this exercise is to teach the reader how to
* combine the use of functions to get more complex behavior out of a program.
*
* My version includes the size of the string in the argument list instead of
* duplicating effort that get_line() does, since it already puts the contents
* into a string and returns the length of the string for me. For strict
* passing of this exercise, reverse() should really only have one argument
* and it should count the size of the string before it works with it. But
* that's prone to issues, such as a string that hasn't been terminated
* properly.
*/
#define MAXLINELENGTH 9001
int get_line(char s[], int limit) {
int c, i;
for (i = 0; i < limit && (c = getchar()) != EOF && c != '\n'; ++i) {
s[i] = c;
}
s[i] = '\0';
/* If I don't include this check, I can't handle blank lines */
if (c == EOF && i == 0) {
return -1;
} else {
return i;
}
}
/* Directly reverse a line's contents. */
void reverse(char input[], int size) {
int tmp;
int i = 0;
size--;
/* If len and i are the same, then there's no reason to proceed */
while (size > i) {
/* Store the first character in a temporary spot... */
tmp = input[i];
/* ... and swap! */
input[i] = input[size];
input[size] = tmp;
/* Bring our numbers closer together */
++i;
--size;
}
}
int main(void) {
/* An int and a string to store each line's data in */
int line_len;
char buffer[MAXLINELENGTH];
while ((line_len = get_line(buffer, MAXLINELENGTH)) != -1) {
reverse(buffer, line_len);
printf("%s\n", buffer);
}
return 0;
}
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