514 - Rails

[sunnycare]

thanks
finally got ac

[Hector_Hsu]

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]

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]

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]

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);
					st.addElement(w);
					idx--;
				}
				cur.removeElementAt(0);
				b.addElement(next);
			} else {
				Integer w = (Integer) st.elementAt(st.size() - 1);
				if (w.equals(next)) {
					st.removeElementAt(st.size() - 1);
					b.addElement(next);
				} else {
					return "No";
				}
			}
		}
		if (cur.size() > 0 || st.size() > 0)
			return "No";
		return "Yes";
	}

Thanks in advance.

[stcheung]

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]

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?

Thanks in advance

Anna

Code: Select all

[quote][/quote]

[Debashis Maitra]

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

[annag]

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]

#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]

Search first..
Don't open a new thread if there is one already

[sangram]

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

[Jan]

Read the problem again.

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.

[sangram]

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]

Well, check the output below...

Output:

Code: Select all

Yes^
No^
^
Yes^
Yes^
Yes^
^
Yes^
^

Here '^' means the newline character. Hope you understand.