Iterated cross sum in C-CodePudding

I am supposed to solve the following problem:

Now write a program to calculate the iterated cross sum. This is calculated by iterating the cross sum until you arrive at a single digit number. Example: 4391873 -> 35 -> 8.

Note: You need nested loops and for understanding what a corss sum does suppose you have the number 14 then its cross sum is 5 = 1 4. Another word may be horizontal checksum.

I have the following code for this, which also calculates simple cross sums, but it doesn't work with the example.

#include <stdio.h>
#include <stdbool.h>

int main()
    {   
    
    int n = 0;
    int c = 0;
    printf("please give us your number: ");
    scanf("%d", &n);
    
   while((c==0) || (c>10)){
    
        while ((n != 0) || (c>10)) {

            if (n % 10 != 0) {

                c = c   n % 10;
                n = n / 10;
            }
            else {
                n = n / 10;
            }

        }
        
   }
    
    printf("%d", c);
    return 0;
   
}

I had thought about linking two while loops, but I can't get it right to calculate the cross sum of the cross sum here. Do you have a tip for this?

Edit: I posted the code.

CodePudding user response：

At each iteration of the outer loop you need to assign C to N and 0 to C. The following solution uses the Ada language.

-- Now write a program to calculate the iterated cross sum.
-- This is calculated by iterating the cross sum until you arrive
-- at a single digit number. Example: 4391873 -> 35 -> 8.
-- Note: You need nested loops.

with Ada.Text_IO;         use Ada.Text_IO;
with Ada.Integer_Text_IO; use Ada.Integer_Text_IO;

procedure Main is
   Num  : Natural;
   Temp : Natural;
   Sum  : Natural := 0;
begin
   Put ("Enter an positive integer: ");
   Get (Num);
   Temp := Num;
   loop
      while Temp > 0 loop
         Sum  := Sum   (Temp rem 10);
         Temp := Temp / 10;
      end loop;
      exit when Sum < 10;
      Temp := Sum;
      Sum  := 0;
   end loop;

   Put_Line ("Original number:" & Num'Image & "  cross sum:" & Sum'Image);
end Main;

You will have to rethink your outer loop termination so that it works using C syntax. The Ada example exits the outer loop before assigning Sum to Temp and 0 to Sum.

CodePudding user response：

You are using a sentinel value of zero in:

while((c==0) || (c>10))

But if I enter 0, this will enter an infinite loop. You want to calculate c from zero from n, then test if c is greater then 9. If it is, than you want to replace n by c. This is not one of the pre-pakaged loops in C, so you probably need break or ,.

while ((n != 0) || (c>10))

The inner loop is just wrong. It should have no dependence on c; get rid of that c>10.

if (n % 10 != 0)

This is a redundant test; 0 % 10 == 0, so this could be simplified.