100 - The 3n + 1 problem

[brianfry713]

Your code is stuck in an infinite loop. Try doing something like this instead:
while(scanf("%d %d",&num1,&num2) == 2) {

[triplemzim]

I used that loop coz in the problem description it is not clear that how many test cases there are. When i used this : while(scanf("%d %d",&num1,&num2)==2) it runs and works well in my compiler but after submitting here it says compilation error....

[brianfry713]

Post your full updated code if you still need help. You have to read until the end of stdin and then terminate. You can click see the reason for your compile error by clicking My Submissions: http://uva.onlinejudge.org/index.php?op ... e&Itemid=9

[triplemzim]

My updated code is here:
#include<stdio.h>

int len(int x)
{
int max;
max=1;
while(x>1)
{
max++;
if(x%2==0) x=x/2;
else x=3*x+1;

}
return max;
}


int main()
{
int i,prev,a,b,max,num1,num2;

while(scanf("%d %d",&num1,&num2)==2)
{

max=0;

a=len(num1);
if(num1==num2) {max=a; goto here;}

for(i=num1;i<=num2;i++)
{

b=len(i);
if(a>b)
{
max=a;
}
else
{
max=b;

a=b;
}
}
here:
printf("%d %d %d\n",num1,num2,max);
}
return 0;
}



now it says wrong answer...

[brianfry713]

i may be greater than j.

[triplemzim]

this same code i just converted in C++ and then got AC what's the problem in ANSI C????

[brianfry713]

Input:

Code: Select all

1 10
10 1

AC output:

Code: Select all

1 10 20
10 1 20

Your code that you posted is failing this I/O. I'd have to see what you changed when converting to explain why your new C++ code is AC. It is possible to solve this problem in ANSI C.

[ron2794]

Here is my code, can you help me in figuring out why this is a Runtime error !

Code: Select all

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
using namespace std;

int *ar,*arr;

int find(unsigned int a,unsigned int u,unsigned int uu){
        int n=1;
        while(a!=1){
                if(a<=uu && a>=u && ar[a-u]!=-1) return (n-1)+ar[a-u];
                if(a%2) a=3*a+1;
                else a/=2;
                n++;
        }
        return n;
}

int main(int argc, char *argv[]){
        int a=1,b=1000000;
        //cout << find(b,a,b)
        int i;

	while(scanf("%d %d",&a,&b)!=EOF){
                ar = (int*)malloc(sizeof(int)*(b-a+1));
                ar=(int*)memset(ar,-1,sizeof(int)*(b-a+1));
                int max=0;
                for(i=a;i<=b;i++){
                        ar[i-a]=find(i,a,b);
                        if(ar[i-a]>max) max=ar[i-a];
                }
                cout << a << " "<< b << " "  << max << endl;
        }
        return 0;
}

[brianfry713]

What if i > j?

[ron2794]

i haven't taken care of that, but that is really a stupid input which i am not expecting at all ....

but if that is the case, what we need to do ?

[ron2794]

phew, thanx, accepted at last !
AC !

[RoniphpBB]

Thanks brianfry713 finally i got AC

[brianfry713]

What if i > j ?

[Ardeshir81]

HI Everyone.
I'm getting WrongAnswer too.
I don't understand why, this is my code :

Code: Select all

//All input integers will be less than 1,000,000 and greater than 0 .
//There will be 2 inputs , i and j , for all integers from i to j we should get the Cycle-Length of '3n + 1' formula and return the maximum .

#include <iostream>

using std :: cout ;
using std :: cin ;
using std :: endl ;

int main ()
{
    int i , j , CL = 1 , maxCL , tmp ; //CL is the Cycle-Length of the current number and maxCL is the maximum Cycle-Length and tmp is the temporary number which the operation will be done on .
    cin >> i >> j ;
    cout << i << " " << j << " " ; //We do not use an extra variable for numbers between i and j , we use the i itself in the for loop , so we'll lose the i at the end of the program .
    if (i > j)
    {
        int swapij ;
        swapij = i ;
        i = j ;
        j = swapij ;
    }
    maxCL = 0 ;
    for ( ; i <= j ; i ++)
    {
        tmp = i ;
        while (tmp > 1)
            if (tmp %2 == 0)
            {
                tmp /= 2 ;
                CL ++ ;
            }
            else
            {
                tmp = tmp * 3 + 1 ;
                CL ++ ;
            }
        if (CL > maxCL)
            maxCL = CL ;
        CL = 1 ;
    }
    cout << maxCL << endl ;
    return 0 ;
}

I compared my answers with the upper post, in this case :
99999 1 525
but I get 999999 1 476

Where of my code is wrong? THNX

[brianfry713]

You need to keep reading sets of i and j until the end of the input, you're only reading one.