How can I solve this problem

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Question:

Complete the program which takes date in number format and then makes its addition of the digits until the
last digit remains single and the print the number as lucky number . eg if input is 777
then 7+7+7 =21 = 2+1 =3 so the answer is 3.

Example1:
Enter the date(ddmmyy):
131083
Your lucky number is:
7
Example2:
Enter the date(ddmmyy):
111111
Your lucky number is:
6

What I have tried:

i tried

Java

<pre>import java.io.*;
class digitsum{ 

public static void main(String arg[])throws Exception
{

    BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
    System.out.println("Enter the date(ddmmyy):");
    int number =Integer.parseInt(br.readLine());


    System.out.println("Your lucky number is:"); 
    //doSum(number);
    System.out.println(doSum(number));
    
   
}//main
    static int doSum(int num)
    {
        int ans=0;
        if(num%10==0)
        {
            return num;
        }
        else
        {
            ans = num%10 + doSum(num/10);
        }
        if(ans<10)
        {
            return ans;
        }
        else
        {
            doSum(ans);
        }
       
        return ans;
    }
}

this code works fine but
for an 777 input it showing 21
but i want
7+7+7 = 21 = 2+1 = "3" as final ans

Posted 8-Mar-18 10:52am

FireMonkey92

Updated 8-Mar-18 12:34pm

PIEBALDconsult

v2

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2 solutions

Solution 3

Java

static int doSum(int num)
{
    int ans=0;
    if(num%10==0) // wrong test try with 7770
    {
        return num;
    }
    else
    {
        ans = num%10 + doSum(num/10);
    }
    if(ans<10)
    {
        return ans;
    }
    else
    {
        doSum(ans); // Here you loose the result of doSum
    }

    return ans;
}

There is a tool that allow you to see what your code is doing, its name is debugger. It is also a great learning tool because it show you reality and you can see which expectation match reality.
When you don't understand what your code is doing or why it does what it does, the answer is debugger.
Use the debugger to see what your code is doing. Just set a breakpoint and see your code performing, the debugger allow you to execute lines 1 by 1 and to inspect variables as it execute.

Debugger - Wikipedia, the free encyclopedia[^]
http://docs.oracle.com/javase/7/docs/technotes/tools/windows/jdb.html[^]
https://www.jetbrains.com/idea/help/debugging-your-first-java-application.html[^]
The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.

Posted 8-Mar-18 12:34pm

Patrice T

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CPallini · Accepted Answer · 2018-03-08T11:15:00

Solution 1

You should return a doSum call:

Java

static int doSum(int n)
{
  if (n <10)
    return n;
  return doSum( n%10 + n/10);
}

Posted 8-Mar-18 11:15am

CPallini

Comments

[no name] 8-Mar-18 17:32pm

My mistake.

CPallini 9-Mar-18 3:10am

By the way, thank you. :-)

[no name] 9-Mar-18 3:24am

Last night I gave you the +5, then ran the code, and it gave the wrong answer. This morning I ran it again and it gave the right answer. :)

CPallini 9-Mar-18 3:43am

You have a quantum computer, don't you? :-)