Use For loop instead of While loop

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In the following program I want to use instead of While loop.
This program returns the sum of individual numbers of positive integer number.

Objective-C

#include<stdio.h>
#include<conio.h>
void main()
{
int num,k,sum=0;
clrscr();
printf("Enter the numbers whose digits are to be added :- ");
scanf("%d",&num);
while(num!=0)
{
k=num%10;
sum=sum+k;
num=num/10;
}
printf("\nSum of the Digits :- %d",sum);
getch();
}

Output
Enter the numbers whose digits are to be added :- 456
Sum of the Digits :- 15

Posted 25-Mar-15 21:26pm

ShailendraDark

Updated 25-Mar-15 21:27pm

v2

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OriginalGriff · Answer 1 · 2015-03-25T21:40:00

Solution 1

Why? While is the natural loop for this. The alternative is basically a while that is harder to read:

C++

for( ; num != 0 ; )
   {
   ...
   }

Posted 25-Mar-15 21:40pm

OriginalGriff

Comments

Stefan_Lang 26-Mar-15 5:25am

Very true, the code doesn't lend itself to a for loop. Therefore I suggested an alternate implementation that, IMHO, is more appropriate to the task, and offers a reasonable application of the for loop.

Stefan_Lang · Answer 2 · 2015-03-25T23:16:00

Typically, for is used when you have a counter controlling the number of times your loop is executed. You don't have such a counter here, although you could construct one.

OriginalGriff did just that in solution 1, using the same variable that your while uses to control the loop. I'd go one step further, since you modify your control variable in each iteration: that is a step typically placed in the last section of the for statement, like this:

C++

for( ; num != 0 ; num = num/10 )
{
   ...
}

Personally, however, I'd do something entirely different: the input is natively entered as a string, so why not read it as a string and simply iterate over the digits that are already present in that string? This would lend itself to a much more natural use of for!

Also, you tagged this question as C++/Objective C, but you are using C functions instead of C++ io streams!?

Additionally, never define main() with a return type of void! the main function should always return int, even though the compiler may accept void. That is a convention expected from every executable program.

Try something like this:

C++

#include <iostream>
#include <string>
int main() {
   string line;
   std::cout << "please enter number: " << std::endl;
   std::getline(std::cin, line);
   int sum = 0;
   for (auto position = line.begin(); position != line.end(); ++position)
   {
      // get character at position, convert to digit, and add to sum
   }
   ...
   return 0; // 0 indicates success; return something else if an error occurs above
}