The process in which a function calls itself directly or indirectly is called recursion and the corresponding function is called a recursive function. Using a recursive algorithm, certain problems can be solved quite easily. A method to solve the number digit problems using recursion is discussed in this article.
Two main components exist for any recursive function are:
- Base Case: A base case is a condition which stops the recursive function calls. A recursive function cannot be formed without a base case because the stack overflow error occurs when the base case is not defined as the function will keep on repeatedly calling itself. For a recursive solution, there can be more than one base case.
- Recursive Case: For all the other conditions apart from the base cases, the function calls itself with a new set of values such that after some finite recursive calls, the function finally calls for a base case and stops itself.
Let’s visualize the recursion by extracting individual digits from a given number. This is the basic step in performing many other mathematical operations.
Below is the implementation to extract every individual digit of a number:
C++
// Recursive function to extract// individual digit for a given// number#include<bits/stdc++.h>using namespace std;void extract(int n){ // If n is a zero // then, stop the recursion if(n == 0) { return; } // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit extract(n / 10); // print the current last digit of the number // with n%10; cout << n % 10 << endl;}// Driver codeint main(){ extract(1234); return 0;}// This code is contributed by 29AjayKumar |
Java
// Recursive function to extract// individual digit for a given // numberimport java.io.*;import java.util.*;class GFG{static void extract(int n){ // If n is a zero // then, stop the recursion if(n == 0) { return; } // Call the function recursively // for n/10 which basically // calls for the remaining number // after removing the last digit extract(n / 10); // print the current last digit of the number // with n%10; System.out.println(n%10);}// Driver codepublic static void main(String[] args){ extract(1234);}}// This code is contributed by Rohit_ranjan |
Python3
# Recursive function to extract# individual digit for a given# numberdef extract(n): # If n is a zero # the stop the recursion if(n == 0): return # Call the function recursively # for n // 10 which basically # calls for the remaining number # after removing the last digit extract(n//10) # print the last digit with n%10 print(n % 10) # Driver codeif __name__ == "__main__": extract(1234) |
C#
// Recursive function to extract// individual digit for a given // numberusing System;class GFG{ static void extract(int n){ // If n is a zero // then, stop the recursion if(n == 0) { return; } // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit extract(n / 10); // print the current last digit of the number // with n%10; Console.Write(n % 10 + "\n");}// Driver codepublic static void Main(String[] args){ extract(1234);}}// This code is contributed by sapnasingh4991 |
Javascript
<script> // Recursive function to extract // individual digit for a given number function extract(n) { // If n is a zero // then stop the recursion if(parseInt(n) == 0) { return; } // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit extract(parseInt(n / 10, 10)); // print the current last digit of the number // with n%10; document.write(n % 10 + "</br>"); } extract(1001);</script> |
Output
1 2 3 4
Similar to this, various other operations can be performed using recursion. Every iterative function can be computed using the recursion.
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