# Sum of digit of a number using recursion

Given a number, we need to find sum of its digits using recursion.
Examples:

```Input : 12345
Output : 15

Input : 45632
Output :20
```

The step-by-step process for a better understanding of how the algorithm works.
Let the number be 12345.
Step 1-> 12345 % 10 which is equal-too 5 + ( send 12345/10 to next step )
Step 2-> 1234 % 10 which is equal-too 4 + ( send 1234/10 to next step )
Step 3-> 123 % 10 which is equal-too 3 + ( send 123/10 to next step )
Step 4-> 12 % 10 which is equal-too 2 + ( send 12/10 to next step )
Step 5-> 1 % 10 which is equal-too 1 + ( send 1/10 to next step )
Step 6-> 0 algorithm stops
following diagram will illustrate the process of recursion

## C++

 `// Recursive C++ program to find sum of digits ` `// of a number ` `#include ` `using` `namespace` `std; `   `// Function to check sum of digit using recursion ` `int` `sum_of_digit(``int` `n) ` `{ ` `    ``if` `(n == 0) ` `    ``return` `0; ` `    ``return` `(n % 10 + sum_of_digit(n / 10)); ` `} `   `// Driven code ` `int` `main() ` `{ ` `    ``int` `num = 12345; ` `    ``int` `result = sum_of_digit(num); ` `    ``cout << ``"Sum of digits in "``<< num ` `       ``<<``" is "``<

## C

 `// Recursive C program to find sum of digits ` `// of a number` `#include `   `// Function to check sum of digit using recursion` `int` `sum_of_digit(``int` `n)` `{` `    ``if` `(n == 0)` `       ``return` `0;` `    ``return` `(n % 10 + sum_of_digit(n / 10));` `}`   `// Driven Program to check above` `int` `main()` `{` `    ``int` `num = 12345;` `    ``int` `result = sum_of_digit(num);` `    ``printf``(``"Sum of digits in %d is %d\n"``, num, result);` `    ``return` `0;` `}`

## Java

 `// Recursive java program to ` `// find sum of digits of a number` `import` `java.io.*;`   `class` `sum_of_digits` `{` `    ``// Function to check sum ` `    ``// of digit using recursion` `    ``static` `int` `sum_of_digit(``int` `n)` `    ``{ ` `        ``if` `(n == ``0``)` `            ``return` `0``;` `        ``return` `(n % ``10` `+ sum_of_digit(n / ``10``));` `    ``}`   `    ``// Driven Program to check above` `    ``public` `static` `void` `main(String args[])` `    ``{` `        ``int` `num = ``12345``;` `        ``int` `result = sum_of_digit(num);` `        ``System.out.println(``"Sum of digits in "` `+ ` `                           ``num + ``" is "` `+ result);` `    ``}` `}`   `// This code is contributed by Anshika Goyal.`

## Python3

 `# Recursive Python3 program to ` `# find sum of digits of a number`   `# Function to check sum of` `# digit using recursion` `def` `sum_of_digit( n ):` `    ``if` `n ``=``=` `0``:` `        ``return` `0` `    ``return` `(n ``%` `10` `+` `sum_of_digit(``int``(n ``/` `10``)))`   `# Driven code to check above` `num ``=` `12345` `result ``=` `sum_of_digit(num)` `print``(``"Sum of digits in"``,num,``"is"``, result)`   `# This code is contributed by "Sharad_Bhardwaj".`

## C#

 `// Recursive C# program to ` `// find sum of digits of a number` `using` `System;`   `class` `GFG {` `    `  `    ``// Function to check sum ` `    ``// of digit using recursion` `    ``static` `int` `sum_of_digit(``int` `n)` `    ``{ ` `        ``if` `(n == 0)` `            ``return` `0;` `            `  `        ``return` `(n % 10 + sum_of_digit(n / 10));` `    ``}`   `    ``// Driven Program to check above` `    ``public` `static` `void` `Main()` `    ``{` `        ``int` `num = 12345;` `        ``int` `result = sum_of_digit(num);` `        ``Console.WriteLine(``"Sum of digits in "` `+ ` `                           ``num + ``" is "` `+ result);` `    ``}` `}`   `// This code is contributed by Anant Agarwal.`

## PHP

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## Javascript

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Output:

`Sum of digits in 12345 is 15`

Besides writing (n==0 , then return 0) in the code given above we can also write it in this manner , there will be no change in the output .

`if(n<10) return n; By writing this there will be no need to call the function for the numbers which are less than 10 `

Time complexity : O(logn) where n is the given number.

Auxiliary space : O(logn) due to recursive stack space.

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