100 - The 3n + 1 problem

[mamun]

I didn't check your code completely. But I see, you haven't considered that first number can be greater than the second.
There are many posts about this topic. Have a look at them.

[Mohammad Mahmudur Rahman]

Your program should be able to read & process multiple test cases. You may try using -

Code: Select all

while(scanf(" %ld %ld",&x,&y)==2)
{
   //process
}

[Mohammad Mahmudur Rahman]

As far as I have seen your program, it should terminate at EOF. Did you provide inputs from stdin or from a file while testing? If from stdin, then press ctrl + Z after all the input sets after the input cases.

[=viki=]

The input haven't only a case.
You must check if x is greater than y or not.
By other hand, you must reuse another post that talk about the same problem, also there are a lot of post about this problem that you can have a look and I'm almost sure that they will resolve your doubts and mistakes.
Good luck!

got AC for prob no. 101 .. now i know for prob 100 end of input is not specified. how long to take the input?

and if x < y then what should i do ... ignore it and take the next input
or stop the prog execution...(no point in printing error msg)...

[=viki=]

now im getting WA for the same code posted above...

now whats the prob ... plz help

[Schutzstaffel]

If x < y then you swap the value of y to x and vice versa or if just use the min(x,y) for x and max(x,y) for y.

[=viki=]

changed my prog but still getting WA plz help..

Code: Select all

#include<stdio.h>


long max=0;
void process(long,long);

int main(void)
	{
         long x,y,a,b;
         while(scanf("%ld%ld",&x,&y)!=EOF){
            if(x>y){
            a=x;
            b=y;
            process(b,a);
         }

         process(x,y);
         printf("%ld  %ld  %ld\n",x,y,max);
         max=0;
         }
	 return 0;
 	}


void process(long x, long y)
	{long i,count=0,n;
	 for(i=x;i<y;i++)
		{
		 n=i;
		 while(1)
		       {
			count++;
			if(max<count)
				max=count;
			if(n==1)
			       {
				count=0;
				break;
			       }

			if((n%2)==0)
				n=n/2;

			else
				n=(3*n)+1;

		       }
		}
	}

whats the problem here now....plz help

[Schutzstaffel]

I think you're a little confused, let's see:

Code: Select all

long x,y,a,b;
         while(scanf("%ld%ld",&x,&y)!=EOF){
            if(x>y){
            a=x;
            b=y;
            process(b,a);
         }

         process(x,y);
         printf("%ld  %ld  %ld\n",x,y,max);
         max=0;
         } 

- You check if x > y, if so you use two variables to get the values of x and y and then process the input in the switched way...ok is correct but why the two extras variables? you can just do process(y,x) if x > y.

- Also if x > y you process with y first and then x (correct), after that you process again with x first and then y (wrong).
You're missing an else statement.

Be sure to test your program before submiting.

[Mohammad Mahmudur Rahman]

Still a lot of error left.
1. Swap (x,y) if x>y.
2. Be carefull about the output format. Your printf statement has extra space charecter which will immediately lead to wrong answer.
3. In the for loop within process, why should you write in this way?-

Code: Select all

for(i=x;i<y;i++)

It must be

Code: Select all

for(i=x;i<=y;i++)

[Emilio]

Schutzstaffel wrote:

If x < y then you swap the value of y to x

For her(I guess) code must swap the values if x > y.

=viki= wrote

how long to take the input?

For example in this manner:

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while (scanf("%d%d",&x,&y)==2)
{
    .....
}

[Schutzstaffel]

It was actually a typo my bad.

[=viki=]

modified my code and got AC thanx for helping......

Code: Select all

oopss  sorry my mistake... :oops: 

[Mohammad Mahmudur Rahman]

Please immediately remove the code. It's not a good practice to leave AC codes on board as others can get AC simply by just copying it & sending to judge.

[Jan]

To =viki=, You should read two numbers until EOF. So, use

Code: Select all

while(scanf("%ld%ld",&x,&y)==2)
{
    //process
}

And remember that x can be greater than y and both can be equal. So, change ..

Code: Select all

void process(long x, long y) 
   {long i,count=0,n;
   if(x>y) 
      //swap x,y 
    for(i=x;i<=y;i++)  //i <= y
      {
          //Remaining code
      }
   }

Hope it helps.

[Red Cent]

Im getting discouraged here.

I know the algorithm. Ive compiled successfully on linux with gcc using the -ansi flag.

But yet Im getting the CE problem.

Here is the code:

/* 3N+1

*/
#include <stdio.h>
#include <stdlib.h>
int cycles(long);
int main (int argc, char **argv)
{
int result = 1;
long i=1;
int stepper = 1, max=1;
long firstnumber, secondnumber;
while (scanf("%ld %ld",&firstnumber, &secondnumber)!=EOF)
{
/*DEBUG
printf("\nfirstnumber = %ld",firstnumber);
printf("\nsecondnumber= %ld\n",secondnumber);
*/
if (firstnumber>secondnumber) stepper = -1;
for (i=firstnumber; i<=secondnumber; i=i+stepper)
{
result = cycles(i);
if (result > max) max=result;
result = 0;
}
printf("%ld %ld %ld\n",firstnumber, secondnumber, max);
firstnumber = 0;
secondnumber = 0;
max =1;
}
}

int cycles(long N)
{
int counter=1;
while (N!=1)
{
if (N%2==0) /*N is even*/
N=N/2;
else /*N is odd*/
N=N*3+1;
counter++;
}
return counter;
}