514 - Rails

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sunnycare
Learning poster
Posts: 74
Joined: Tue Mar 08, 2005 2:35 am
Location: China , Shanghai
thanks
finally got ac

Hector_Hsu
New poster
Posts: 13
Joined: Thu May 26, 2005 1:16 pm

514 - Rails : why WA?

My algorithm is to create a "stack" ,
and required permutation stored in a array named "permutation"
After input,
I check number 1 to N in a for loop
if number i entered now and the permutation need him now,
the permutation index changes to the next index and check if there are other can be pop from the stack.
finally,if stack has 0 element ->ans is Yes
else -> No

[sorry for my poor english (- -")]
-------------------------------------------------------------

Code: Select all

``````#include<iostream>
using namespace std;
int main(void)
{
int N,i,stack[1001],permutation[1001],top,per,j;
while(cin>>N&&N)
{
while(cin>>permutation[1])
{
if(permutation[1]!=0)
{
for(i=2;i<=N;i++)
cin>>permutation[i];
top = 0;
per = 1;
for(i=1;i<=N;i++)
{
if(permutation[per]==i)
{
per++;
while(permutation[per]==stack[top])
{
top--;
per++;
}
}
else
{
top++;
stack[top] = i;
}
}
if(top==0)
cout<<"Yes"<<endl;
else
cout<<"No"<<endl;
}
else
{
cout<<endl;
break;
}
}
}
return 0;
}
``````

Wei-Ming Chen
Experienced poster
Posts: 122
Joined: Sun Nov 13, 2005 10:25 am
Location: Taiwan
I'm sorry, your code is right.
But have one thing to attention:

if(permutation[per]==i)
{
per++;
while(permutation[per]==stack[top])
{
top--;
per++;
}
}

When you do top--;
Maybe top will come to 0!! this is why you got WA
so you can change the code to

if(permutation[per]==i)
{
per++;
while(permutation[per]==stack[top] && top>0)
{
top--;
per++;
}
}

then I think you will get AC

Sayeef
New poster
Posts: 12
Joined: Sun Jun 18, 2006 3:06 am

514 WA

This is my code . I keep getting WA. why is that?? Can any one tell me?

Code: Select all

``````#include<stdio.h>
void push(int);
int pop(void);
int stack[1001]={0},top=0;
void main()
{
int noc=0;
for(;;)
{
scanf("%d",&noc);
if(noc==0)
break;
for(;;)
{
int rail[1001]={0},i,flag=0,j,diff=0,large=0,k=1,p;
scanf("%d",&rail[1]);
if(rail[1]==0)
break;
for(i=2;i<=noc;i++)
scanf("%d",&rail[i]);
for(j=0;j<noc;j++)
{
if(rail[j]<rail[j+1])
{
diff=rail[j+1]-large;
for(p=1;p<diff;p++)
push(large+(k++));
large=rail[j+1];
k=1;
}
else if(rail[j]>rail[j+1])
{
if(rail[j+1]!=pop())
{
flag=1;
break;
}
}
}
if(!flag)
printf("Yes\n");
else if(flag==1)
printf("No\n");

}
printf("\n");
}
}
void push(int data)
{
stack[++top]=data;

}
int pop()
{
int temp;
temp=stack[top];
top--;
return temp;
}
``````

icesoft85
New poster
Posts: 4
Joined: Sun Mar 26, 2006 5:51 am
Contact:

514 - Algorithm error?

Hello everyone!

I've tested my solution with tan_Yui test data and it works all right. I only make a simulation of the problem. Sorry for posting code, but really, I couldn't find the mistake.

I would be glad if some test data is sent or if someone could check the algorithm, maybe I'm forgetting somethign.

cur is the current order = 1, 2, 3, ... n
des is the desired order = a1, a2, a3, ..., an

Code: Select all

``````String solve(Vector cur, Vector des) {
Vector st = new Vector();
Vector b = new Vector();
for (int i = 0; i < des.size(); i++) {
Integer next = (Integer) des.elementAt(i);
int idx = cur.indexOf(next);
if (idx >= 0) {
while (idx > 0) {
Integer w = (Integer) cur.elementAt(0);
cur.removeElementAt(0);
idx--;
}
cur.removeElementAt(0);
} else {
Integer w = (Integer) st.elementAt(st.size() - 1);
if (w.equals(next)) {
st.removeElementAt(st.size() - 1);
} else {
return "No";
}
}
}
if (cur.size() > 0 || st.size() > 0)
return "No";
return "Yes";
}``````

stcheung
Experienced poster
Posts: 114
Joined: Mon Nov 18, 2002 6:48 am
Contact:
One thing I notice is that you didn't seem to clear the contents of your stack array after you are done processing 1 line of input.

Another thing is that your code seems more complicated than needed, due to your approach. For instance, you don't really need to implement stack. (I solved this with just 2 arrays). Try to come up with a simpler approach and that might be faster than trying to debug this particular piece of code.

annag
New poster
Posts: 2
Joined: Tue Jan 16, 2007 9:21 pm

514 - Rails, why PE?

Hi.

I have submitted the solution for this problem 5 times, and every time I get a “Presentation Error”, but really don’t understand why. I format the output as it told in the problem description: “there is one empty line after the lines corresponding to one block of the input file”. And as the last “non-null” block is also a block, it also must be followed by an empty line. So having such an input:

#Beginning
5
1 2 3 4 5
5 4 1 2 3
0
6
6 5 4 3 2 1
0
0
#End

we must get this output:

#Beginning
Yes
No

Yes

#End

Note the empty line after the last answer. But written in this way, I get PE, so I’ve also tried to eliminate the last empty line, but this retrieves the same error. I can guarantee that don’t add redundant spaces anywhere. So, where am I mistaken? I’m new to this site, and I wonder if it’s possible to obtain the test case and the result, because of which PE occurs?

Anna [quote][/quote]

Debashis Maitra
Learning poster
Posts: 62
Joined: Sun Jul 09, 2006 8:31 am
Location: University of Dhaka
Contact:
for your input my output is

Code: Select all

``````Yes
No
<===blank line
Yes
<===blank line
<=== cursor is here

``````
this may help u

best of luck
Akash chhoyar swopno
Dream to touch the sky

annag
New poster
Posts: 2
Joined: Tue Jan 16, 2007 9:21 pm
Debashis Maitra wrote:for your input my output is

Code: Select all

``````Yes
No
<===blank line
Yes
<===blank line
<=== cursor is here

``````
this may help u

best of luck
Yea, it worked, thank you very much.

ishtiaq ahmed
Learning poster
Posts: 53
Joined: Sat Jul 29, 2006 7:33 am

#include<stdio.h>
void main()
{
int i,j,ish[1000000],ash[1000000],tot,index,count,aa,dex,k,m;
for(;;)
{
scanf("%d",&tot);
if(tot==0)
break;
for(;;)
{
index=0;dex=0;
for(i=1;i<=tot;i++)
{
scanf("%d",&ish[index=index+1]);
if(ish[index]==0)
break;
}
if(ish[index]==0)
break;
count=1;j=1;
while(count<=tot)
{
if(ish[j]!=count)
ash[dex=dex+1]=count;
if(ish[j]==count)
{
if(dex<count && j<count)
{
k=j;
for(m=dex;m>=1;m--)
{
if(ash[m]!=ish[k+1])
{
printf("No\n");
goto aa;
}
k++;
}
}
j++;
}
count++;
}
printf("Yes\n");
aa:
}
printf("\n");
}
}

helloneo
Guru
Posts: 516
Joined: Mon Jul 04, 2005 6:30 am
Location: Seoul, Korea
Search first..

sangram
New poster
Posts: 8
Joined: Fri Jun 30, 2006 3:27 pm
Contact:

Getting WA - someone please provide test cases or explain

I have solved the problem using a simulation using stacks. Please point out any mistake.

Thanks.

Code: Select all

``````Removing the code .. as it was giving AC
``````
Last edited by sangram on Thu Sep 20, 2007 11:31 pm, edited 1 time in total.

Jan
Guru
Posts: 1334
Joined: Wed Jun 22, 2005 10:58 pm
Contact:
there is one empty line after the lines corresponding to one block of the input file
But you are printing a blank line between cases. Print a blank line after each case.

Hope it helps.
Ami ekhono shopno dekhi...
HomePage

sangram
New poster
Posts: 8
Joined: Fri Jun 30, 2006 3:27 pm
Contact:

Hi,
I didn't really understand what you meant.
I tried with the sample data as follows:

Code: Select all

``````5
1 2 3 4 5
5 4 1 2 3
0
6
6 5 4 3 2 1
5 6 4 3 2 1
1 2 3 4 5 6
0
10
1 2 3 4 5 10 9 8 7 6
0
0
``````
This produced the output as follows:

Code: Select all

``````Yes
No

Yes
Yes
Yes

Yes
``````
Please tell me if this is wrong.

Thanks,
Sangram

Jan
Guru
Posts: 1334
Joined: Wed Jun 22, 2005 10:58 pm
Contact:
Well, check the output below...

Output:

Code: Select all

``````Yes^
No^
^
Yes^
Yes^
Yes^
^
Yes^
^``````
Here '^' means the newline character. Hope you understand.
Ami ekhono shopno dekhi...
HomePage