I came across these two statements in a SNS photo album, with the title "the most elegant way of output I ever met" or something.
Here are the two statements:
printf("%d%c", a, " \n"[i==n]);
puts("YES\0No"+condition * 4);
I've no idea what they are doing and how they work. Will someone explain to me? Thank you.
" \n"[i==n] takes the expression i==n, which evaluates to either 0 or 1, and uses it as an index into the array " \n", obtaining either ' ' or '\n'.
"YES\0N0"+condition * 4 takes the array "YES\0N0", which 'decays' to a pointer to its first element when used in most expressions, including this one, and adds condition * 4 to this pointer. If condition is 1, that yields a pointer to the 'N' at the beginning of "N0".
If i != n, a space is printed after %d, else a line-feed.
// printf("%d%c", a, " \n"[i==n]);
// when i != n
printf("%d%c", a, " \n"[0]); // or
printf("%d%c", a, ' '); // or
printf("%d ", a); // or
// when i == n
printf("%d%c", a, " \n"[1]); // or
printf("%d%c", a, '\n'); // or
printf("%d\n", a); // or
An interesting way to print a number separator, likely use in a for loop.
Similar for puts("YES\0N0"+condition * 4);
When condition is 0, it prints
puts("YES");`
When condition is 1, it prints
puts("N0");` // Thanks @ Jonathan Leffler