What are the bugs in this function?

Question

#include <string.h>
#include <stdlib.h>
char *reverse(char *input) {
int len = strlen(input);
char output[len];
for (int i = 0; i < len; i++) {
output [len - i - 1] = input[i];
}
return output;
}

Answer 1

Rose Candy ,

this looks very much like a homework or something like this. please do a try by yourself first.

thanks for your understanding!

Answer 2

Lets look at this:

char *reverse(char *input) {
int len = strlen(input);
char output[len];

for (int i = 0; i < len; i++) {
output [len - i - 1] = input[i];
}

return output;

}

Lets use "Hello" for the input

len now = 5
output = memory-location 1, 2, 3, 4, 5 (named output[0], output[1], ect) probably filled with garbage values

__ __ __ __ __
|__| |__| |__| |__| |__| << 5 memory locations for output

within the scope of the for:

i = 0 initialized; Going to test if i less than 5; then increment i each iteration;

first pass:
output[5 - 0 - 1] (this is equal to 4) becomes input[0]

__ __ __ __ __
|__| |__| |__| |__ | |H |

pass two, three, four and five will result in:

__ __ __ __ __
|o | |l | |l | |e | |H |

You want to end strings with a '\0' terminating char.

1. How will you add that?
2. Your current array cannot handle it