3 ms·

if(n&1) else

• imtringued 10mo ago
  You can do it even faster with the if statements: #include <stdio.h> #include <stdlib.h> int main(int argc, char *argv[]) { if (argc < 2) { fprintf(stderr, "Usage: %s <string>\n", argv[0]); return 1; } char *s = argv[1]; int i; /* find the end of the string */ for (i = 0; s[i] != '\0'; ++i) ; /* make sure the string wasn't empty */ if (i == 0) { fprintf(stderr, "Error: empty string\n"); return 1; } /* last character is at s[i - 1] */ char d = s[i - 1]; if (d == '0') printf("even\n"); if (d == '1') printf("odd\n"); if (d == '2') printf("even\n"); if (d == '3') printf("odd\n"); if (d == '4') printf("even\n"); if (d == '5') printf("odd\n"); if (d == '6') printf("even\n"); if (d == '7') printf("odd\n"); if (d == '8') printf("even\n"); if (d == '9') printf("odd\n"); return 0; } gcc -std=c11 -Wall -Wextra -O2 -o check_digit check_digit.c ./check_digit 999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999
  • Tistron 10mo ago
    You can do it even even faster by replacing your if statements (works because the ascii values end in the digit they represent): if (d & 1) printf("odd\n"); else printf("even\n")
  • wiz21c 10mo ago
    I'm disappointed, it's not in rust. :-)
    • actionfromafar 10mo ago
      Still hoping for the C++ template version. Don’t pay for what you don’t use!
  • tetris11 10mo ago
    probably easier in bash: number="$1" if [[ "$number" =~ "^(2|4|6|8|10|12|14|16|18|20)$" ]]; then echo even elif [[ "$number" =~ "^(1|3|5|7|9|11|13|15|17|19)$" ]]; then echo odd else echo Nan fi A bit limited, but you can scale it up
    • teo_zero 10mo ago
      Scaled up: case "$1" in *0|*2|*4|*6|*8) echo even;; *) echo odd;; esac If $1 had a trailing non-digit, or was empty, that would indeed be an odd situation!
  • d-lisp 10mo ago
    You inspired me this joyful rewrite: #define _(e) { e;}; #define r(e) _(return e) #define I(b, e) _(if (b) r(e)); #define W(e) _(while (1) _(e)); int main(int c, char **v) { _(I(c != 2, -1) _(c = 0) W(I(!v[1][c++], v[1][c - 2] & 1))) }