Member Avatar for biljith

isnt this the shortest method

#include<iostream.h>
#include<conio.h>
void main()
{
 clrscr();
 int a,i=0;
 cout<<"enter a number";
 cin>>a;
 while(a>0)
 {
  int b=a%10;
  a=a/10;
  i=i+b;
 }
cout<<"sum="<<i;
getch();
}
Edited by peter_budo because: Keep It Clear - Do wrap your programming code blocks within [code] ... [/code] tags
  • 9 Contributors
  • 11 Replies
  • 284 Views
  • 3 Years Discussion Span
  • Latest Post Latest Post by ReaseySo

Dani AI

Generated

The thread mixes two different tasks: reversing a number’s digits and summing its digits. ’s original loop accumulates digit values (the digit sum), as noticed, while the title asks for digit reversal — called out that mismatch. Several replies show Python/C idioms; for C++ prefer standard headers and int main() rather than old iostream.h/conio.h and void main().

A concise, robust C++ approach is to treat the input as a string (handles very large numbers and preserves any leading zeros when desired), extract digits, compute the sum, and produce both a string-style reversal and a numeric-style reversal (trim leading zeros):

#include <iostream>
#include <string>
#include <algorithm>
#include <cctype>

int main() {
    std::string s;
    if (!(std::cin >> s)) return 0;
    bool negative = !s.empty() && s[0] == '-';
    std::string digits;
    for (char ch : s) if (std::isdigit(static_cast<unsigned char>(ch))) digits.push_back(ch);

    int sum = 0;
    for (char d : digits) sum += d - '0';

    std::string rev = digits;
    std::reverse(rev.begin(), rev.end());

    std::string rev_trim = rev;
    rev_trim.erase(0, rev_trim.find_first_not_of('0'));
    if (rev_trim.empty()) rev_trim = "0";

    if (negative) std::cout << '-';
    std::cout << rev_trim << "  (reversed as number)\n";
    std::cout << rev << "  (reversed as string, keeps zeros)\n";
    std::cout << "sum=" << sum << '\n';
    return 0;
}

Notes and cautions: the string method accepts arbitrarily long input and is simple to reason about; an arithmetic reversal (multiply-then-add) is slightly faster and uses constant memory but risks overflow for large inputs (see ’s numeric example). What “shorter” means was raised by — brevity in source text often trades readability or safety. Decide whether reversed output should preserve leading zeros or represent a numeric value, and choose the string or numeric method accordingly.

Recommended Answers

All 11 Replies

Member Avatar for TrustyTony

Doesn't look Python code for me!

from sys import stdout
def rev(a):
    while a:
        a, d = divmod(a,10)
        stdout.write(d)

rev(int(raw_input('Give number: ')))
Edited by TrustyTony because: n/a
commented: Why should it be Python in a C++ forum? -3
Member Avatar for woooee

i=i+b;
This will give you the sum of the digits. Add some print statements so you know what is going on.

Member Avatar for snippsat

isnt this the shortest method

Not when you post C code in python forum.

>>> raw_input('enter a number: ')[::-1]
enter a number: 1234
'4321'
Member Avatar for TrustyTony

Not when you post C code in python forum.

>>> raw_input('enter a number: ')[::-1]
enter a number: 1234
'4321'

How true! That accepts anything (in spirit of duck typing), not only number, prints those distracting quotes, however. Hmmm. Lets make it full program:

print(' '.join(((raw_input('Anything ')[::-1]) ,'reversed.')))

:icon_wink:

Edited by TrustyTony because: n/a
Member Avatar for peter_budo

Moved to C section

Member Avatar for WaltP

And moved again to C++

Member Avatar for arkoenig

And now that it's in the C++ forum, I can point out that the title of this thread talks about printing the reverse of a number, but the program computes the sum of its (decimal) digits. Which is right?

Member Avatar for peter_budo

And now that it's in the C++ forum, I can point out that the title of this thread talks about printing the reverse of a number, but the program computes the sum of its (decimal) digits. Which is right?

It will be down to whatever that program is doing. I had to reuse title of original thread where this was hijaked. Sorry for misleading info, but OP wasn't helpful with his descriptions, plus it was long time I had to do anything with C or C++ code (hence why it was moved to C and then to C++)

Member Avatar for biljith

sorry guys fr the mistake but is there any shorter method to print sum of individual decimals(talking of c++)

Member Avatar for Sky Diploma

What exactly does the OP mean by shorter?
Shorter in code ? Or Shorter in execution time ? Or something else?
I dont see why there is a need to change the current program into something shorter.
However, I would sure recommend you to use a newer compiler.

Member Avatar for ReaseySo 
#include <stdio.h>

int main()
{
   int n, reverse = 0;

   printf("Enter a number to reverse\n");
   scanf("%d",&n);

   while (n != 0)
   {
      reverse = reverse * 10;
      reverse = reverse + n%10;
      n = n/10;
   }

   printf("Reverse of entered number is = %d\n", reverse);

   return 0;
}
Be a part of the DaniWeb community

We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.