For statement in CPossible Duplicate: Help with C puzzle [1]
This morning i had a job interview and they gave me this problem:
You should change one character to print "*" 42 times. You can replace, add or remove ONLY one character.
Still i cant figured it, i've tried over and over again.
#include <stdio.h>
main(){
int i,n = 42;
for(i = 0; i < n; i--){
printf("*");
}
}
One option would be to change the < to a +:
#include <stdio.h>
main(){
int i,n = 42;
for(i = 0; i + n; i--){
printf("*");
}
}
The reason this works is that C treats nonzero values as "true" and zero values as "false." The value of i + n starts at 42 and then counts down 41, 40, 39, ..., 1, 0. When it hits zero, it must mean that i == -n, at which point you're done.
-i or n-- - Henk Holterman
ACCEPTED]
#include <stdio.h>
main(){
int i,n = 42;
for(i = 0; -i < n; i--){ //added a minus here
printf("*");
}
}
But to be honest, I think that this is a silly interview question.
for(i = 0; i < n; n--){
printf("*");
}
Looks like you change the i-- to n--.
Seems like a strange interview question. What was it for, if you don't mind me asking?
What about changing the - to a +? :)
I changed the source a tiny little bit.
$ cat 4927230.c
#include <stdio.h>
int main(void) {
int i, n = 42;
for (i = 0; i < n; i--) {
printf("*");
}
puts("");
return 0;
}
$ tr \- \+ < 4927230.c | gcc -xc - && ./a.out
******************************************
$
hehe
tr does, scratches his/her head, and says "umm... you pass". Total score = +1 - Mike
How about:
for(i = 0; -i < n; i--) {
^
That's easy:
#include <stdio.h>
main(){
int i,n = 42;
for(i = 0; i < n; n--){
printf("*");
}
}
While this is a "puzzle" rather than a programming task, I think it is actually a rather good interview question, as it tests a number of skills valuable in a programmer. If you can't solve this, then you may have a lot of trouble reasoning about complex code.
The first thing I noted is that i is initialized twice, so its initialization to 42 is irrelevant unless the second initialization is eliminated, e.g. by changing it to i + 0. The next thing I noted is that we're stuck with -- as it cannot be usefully modified by a single character. So we're decrementing a counter but using < for the test, so we need to do an inversion of some sort. -i < n does that handily, as does n-- by decrementing the limit rather than the counter. The i + n solution, which is equivalent to -i != n, is harder to come up with.
-flipping a<or adding a!... That said I still couldn't work it out. Seems like a fair test of my (in)ability to quickly gauge what tools are available and how to apply them within narrow constraints. - J. Winchesteri--=>i++) so you have code that is a little bit more readable". If that doesn't get you the points, you don't want the job anyway. - JeremyP