3 ms·
I know it's silly, but I just want to fix his first version with the minimum possible changes; /* Copyright 2023. All unauthorized distribution of this sourc
by billforsternz 10mo ago
I know it's silly, but I just want to fix his first version with the minimum possible changes;
/* Copyright 2023. All unauthorized distribution of this source code
will be persecuted to the fullest extent of the law*/
#include <stdio.h>
#include <stdint.h>
#include <string.h>
int main(int argc, char* argv[])
{
uint8_t number = argc>1 ? argv[1][strlen(argv[1])-1]-'0' : printf("Usage: odd-or-even number\n");
if (number == 0)
printf("even\n");
if (number == 1)
printf("odd\n");
if (number == 2)
printf("even\n");
if (number == 3)
printf("odd\n");
if (number == 4)
printf("even\n");
if (number == 5)
printf("odd\n");
if (number == 6)
printf("even\n");
if (number == 7)
printf("odd\n");
if (number == 8)
printf("even\n");
if (number == 9)
printf("odd\n");
if (number == 10)
printf("even\n");
}
This way it basically works. It's a shame that it doesn't call out a non numeric argument but that's about the only problem. It relies on a trick, printf() returns the number of characters printed, so the error message string needs to be longer than 10.
- pcthrowaway 10mo agoWouldn't using elif for all comparisons after the first improve performance? Or is the performance considered worse because it becomes O(n) (where n < MAX_UINT) vs. constant time ( O(MAX_UINT) )
- billforsternz 10mo agoIt certainly would be normal to use else if (or switch) if you wanted to be picky but really such changes are inconsequential here. And I was trying to change just one line. Sadly I also had to quietly change stdlib.h to string.h as well.
- LegionMammal978 10mo agoIf you wanted to avoid <string.h>, you could use the poor man's strlen(), snprintf(0,0,"%s",argv[1]). For full input validation without adding any more statements, the best I can get (in ISO C) is uint8_t number = (argc<2||sscanf(*++argv,"%*[0123456789]%n",&argc)||argc--[*argv]?printf("bad\n"):argc[*argv])-'0'; // No problems here Though with either function you may run into issues if the OS allows arguments longer than INT_MAX. To be defensive, you could use "%32767s" or "%*32767[0123456789]%n" instead, at the cost of failing inputs longer than 32KiB.
- billforsternz 10mo agoMarvellous, love it. Thank you.