10773 - Back to Intermediate Math

[TISARKER]

Please Tell me why the following code gives wrong answer ?

#include<stdio.h>
#include<math.h>
#define type int
#define dtype double
void main()
{
type i,n;
dtype u,v,d;
//freopen("F:\\input.txt","r",stdin);
//freopen("F:\\myput.txt","w",stdout);

scanf("%d",&n);n++;
for(i=1;i<n;i++)
{
scanf("%lf%d%d",&d,&v,&u);
if((u>v)&&(u!=0)&&(v!=0))
printf("Case %d: %.3lf\n",i,an expresion));
else printf("can't determine\n");
}

}

[little joey]

Why don't you use formatting tags when posting code? Is much nicer to read.

Print "Case x: can't determine".
I have no clue why they always want us to print those stupid case numbers, but they do, and they're the boss...

[TISARKER]

I cann't use formatting tags when posting code?
I want to know it.
Finally I got accpted and I also think it about Boss.

***Its all correct whatever the do/wish.
***Its none correct whatever we do/wish Because we are not Boss.

[Adrian Kuegel]

Print "Case x: can't determine".
I have no clue why they always want us to print those stupid case numbers, but they do, and they're the boss...

It helps the judges in a realtime contest with judging (they have to look at your output). Of course it doesn't make much sense in a online contest. But for example I proposed my problem originally for a realtime contest, but it was not used there.
It also helps during the preparation of a contest, if one of the judge solutions is wrong to find the test case.

[little joey]

Thank you for explaining. It makes sense.

[Niaz]

Though I got it accepted still I have some confusion about Straight Crossing. Why the river's velocity is ignored here ? There must be an effect of river's velocity.

For Anupam only : There is a math problem in Tofajjal Sir's Physics Book in HSC Level. At that math, it is shown that a boat can cross a river in two ways (as you said in your problem) and there the velocity of river is considered in both the cases. But the solution for your problem can not work with that problem. Would you please explain this matter clearly. Thanks in advance.

[anupam]

For Anupam only : There is a math problem in Tofajjal Sir's Physics Book in HSC Level. At that math, it is shown that a boat can cross a river in two ways (as you said in your problem) and there the velocity of river is considered in both the cases. But the solution for your problem can not work with that problem. Would you please explain this matter clearly. Thanks in advance.

Thanks Niaz for your attention. I had done all the example of all the physics books of HSC level to get chance at CSE, BUET. So, for you only:
(better if I could draw a figure)
There are two vel.s (your boat's and river's). For straight crossing, you should start we angle theta with river's flow direction and ofcourse, theta>90 so that the resultant vel. is in the straight direction. Now, just think, do the vel. of river helps you to cross any distance across the river??? It is only the component of your boat in the vertical direction. The vel. of river helps to pass distances horizontally. So, there is no need for the river's velocity for this case. Am i clear? I am now not regular to board for some days. So, if you need further clarification send me mail at abrbuet@yahoo.com

[Niaz]

Anupam,
Thanks for your reply. Actually still I have some confutations (may be that is why I did not get the chance in BUET ). I am going to Malaysia for attending World Universities Debating Championship on 26th December. Insha-Allah I will be beck by 5th of January. Then I will mail you.
Niaz

NB : Though I have confusions, during contest time from my team I attacked this problem and solved it.

[rajsekar_manokaran]

I kept getting WA when my code checked for `can't determine' like this:

Code: Select all

	if (v>=u)
	    printf ("can't determine\n");

then i changed it to

Code: Select all

	if (v>=u || u==0 || v==0)
	    printf ("can't determine\n");

and got AC

isn't the first one correct?
when v == 0 (the river is still), i can determine the time difference which would turn out to be zero.

[Morning]

Code: Select all

#include <iostream>
#include <cmath>
#include <cstdio>
using namespace std;
int main()
{
	int N;
	double d,v,u;
	while(cin >> N)
	{
		for(int i = 1;i <= N;i++)
		{
			cin >> d >> v >> u;
			if(v == 0 || u == 0 || u <= v) ...			else
			{
				...			}
		}
	}
	return 0;
}

a quite simple problem,huh?why do i keep getting WA???

[Sanny]

if(v == 0 || u == 0 || u <= v) printf("Case %d: can't determine\n",i);

I think v=0 is valid.

[Morning]

i don't think so.

i've changed my code to if(u == 0 || u <= v) printf("Case %d: can't determine\n",i);

but still got WA

[Morning]

i know why i keep getting WA

the input must be weird

i deleted my while(cin >> N) loop and got AC

but i still don't know why

if there's something following the input case ,i should get TLE but not WA
:-?

[rimu]

this ridiculously easy problem gave me wrong answer for a
week. so, had to look for threads to find what's wrong. what
i've found is really "STUPID "

i got AC when i used the condition if v ( river's velocity ) == 0
output " can't determine " !!!!!!!!!!!!!!!!!!

could someone who has used the condition( realising its reason )
or better if the problemsetter explain me why i can't
determine the required time difference when the rivers velocity
is zero???????? ( if i'm not wrong ( which is pretty obvious )
in that case shortest path and shortest time would require
the same time and result should be zero )

[little joey]

Because that is exactly what is asked:

and then print "can't determine" (without the quotes) if it is not possible to find different paths

If v==0, there is only one path, and not two different paths, so the answer is "can't determine".

Please check carefully if you fully understand the description before you start screaming on the board...