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 single digit // number, then print the // digit and break stop // the recursion if(n / 10 == 0) { cout << n; return; } // If n is not a single // digit number, then // print the last digit cout << n % 10 << endl; // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit return extract(n / 10);} // Driver codeint main(){ extract(1001); return 0;} // This code is contributed by 29AjayKumar |
Java
// Recursive function to extract// individual digit for a given // numberclass GFG{ static void extract(int n){ // If n is a single digit // number, then print the // digit and break stop // the recursion if(n / 10 == 0) { System.out.print(n); return; } // If n is not a single // digit number, then // print the last digit System.out.print(n % 10 + "\n"); // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit extract(n / 10);} // Driver codepublic static void main(String[] args){ extract(1001);}} // This code is contributed by Rohit_ranjan |
Python3
# Recursive function to extract# individual digit for a given# numberdef extract(n): # If n is a single digit # number, then print the # digit and break stop # the recursion if(n//10 == 0): print(n) return # If n is not a single # digit number, then # print the last digit print(n % 10) # Call the function recursively # for n // 10 which basically # calls for the remaining number # after removing the last digit return extract(n//10) # Driver codeif __name__ == "__main__": extract(1001) |
C#
// Recursive function to extract// individual digit for a given // numberusing System; class GFG{ static void extract(int n){ // If n is a single digit // number, then print the // digit and break stop // the recursion if(n / 10 == 0) { Console.Write(n); return; } // If n is not a single // digit number, then // print the last digit Console.Write(n % 10 + "\n"); // Call the function recursively // for n // 10 which basically // calls for the remaining number // after removing the last digit extract(n / 10);} // Driver codepublic static void Main(String[] args){ extract(1001);}} // This code is contributed by sapnasingh4991 |
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Similar to this, various other operations can be performed using recursion. Every iterative function can be computed using the recursion.
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