stone game one solution works and the other doesn't, why?

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1

Hi, I solved the Stone Game problem with this solution: http://www.codechef.com/viewsolution/1101333

I’m trying to solve it getting input with gets.

The sample input works well, but the solution doesn’t pass codechef test.

This is one of the solutions that don’t work: http://www.codechef.com/viewsolution/1101396

Could you help me understanding why?

Thank you.

1 Like
2

use that code for input generation and than run your not working code

#include <cstdio>

int main() {
	printf( "%d\r\n", 2);
	printf( "%d\r\n", 2);
	printf( "%d %d\r\n", 1, 2);
	printf( "%d\r\n", 3);
	printf( "%d %d %d\r\n", 1, 2, 3);
	return 0;
}

it returns “BOB”, “BOB”, but it has to be “BOB”, “ALICE”, quite hard to find…

1 Like
3

@beautybrain why did you vote down my answer? is it incorrect?

4

It gives me a segmentation fault, because you first say “1 test case, 100 piles” but then you enter 1000 stones FOR 1000 piles (the for condition is wrong, it should be ‘i<100’ instead of ‘i<1000’), right?

After I’ve corrected that, the answer is the same as the other solution. 1 says bob, and the “wrong” solution says bob too. I’m still stuck at understanding why my other solution is wrong :frowning: I made the buffer 500 elements big, because in the “biggest” scenario… I would need 5 char 100 times, like '1000 '. But, when the last ‘1000’ comes, it would have a ‘\0’ instead of a ’ ’ after it.

5

I’m sorry about the incorrect code before, it’s updated, try now :wink:

6

So the problem was in the additional escape sequence ‘\r’ ?
The getchar()s only ate the ‘\r’, leaving the ‘\n’ in the input buffer.
So the gets() would only get a ‘\n’ and continue to the next test case.
Was this the problem? :stuck_out_tongue:

I fixed it with a double getchar() after every Enter (I suppose I could also use a loop like while((ch = getchar()) != EOF && ch != ‘\n’); right before the gets() call).

Thank you!