Recursion is a programming technique that involves defining a problem (or the solution to a problem) in terms of itself. It is a method of solving a computational problem where the solution depends on solutions to smaller instances of the same problem. Recursion comes directly from Mathematics, where there are many examples of expressions written in terms of themselves. A recursive function solves a particular problem by calling a copy of itself and solving smaller subproblems of the original problem. Many more recursive calls can be generated as and when required. It is essential to know that we should provide a certain case to terminate this recursion process.
Recursion provides a clean and simple way to write code. Some problems are inherently recursive like tree traversals, Tower of Hanoi, etc. For such problems, it is preferred to write recursive code. We can write such codes also iteratively with the help of stacks and queues, but the code becomes complex and difficult to understand.
In a recursive algorithm, the computer "remembers" every previous state of the problem. This information is "held" by the computer on the "activation stack" (i.e., inside of each functions workspace). Every function has its own workspace PER CALL of the function.
Recursion is a widely used idea in data structures and algorithms to solve complex problems by breaking them down into simpler ones. An important application of recursion in computer science is in defining dynamic data structures such as lists and trees. Recursive data structures).
Properties of Recursion:
- Performing the same operations multiple times with different inputs.
- In every step, we try smaller inputs to make the problem smaller.
- Base condition is needed to stop the recursion otherwise infinite loop will occur.
An example of implementing recursion in Python is:
#include <iostream>
using namespace std;
int factorial(int n)
{
// Base case: if n is 0 or 1, return 1
if (n == 0 || n == 1)
return 1;
// Recursive case: if n is greater than 1,
// then recursively call factorial of n-1
return n * factorial(n - 1);
}
In summary, recursion is a programming technique that involves defining a problem in terms of itself. It is a method of solving a computational problem where the solution depends on solutions to smaller instances of the same problem. Recursion provides a clean and simple way to write code, and it is widely used in data structures and algorithms to solve complex problems by breaking them down into simpler ones.
