Difference Between Recursion and Iteration
Recursion is a technique in which the function calls itself in its body to solve the problem, typically breaking into smaller and more manageable sub-problems. In contrast, iteration is a technique that repetitively executes a code block until the condition is unmet. This article will briefly discuss the difference between recursion and iteration.
Recursion and Iteration are two important concepts of programming where we need to repetitively do certain operations until the given condition is not met. In recursion, the function calls itself in its body to solve the problem, typically breaking into smaller and more manageable sub-problems. In contrast, Iteration is a technique that repetitively executes a code block until the condition is unmet.
Both are used where we need repetition of certain operations, but both are different in the Control Structure, Space Complexity, Performance, etc.
In this article, we will learn how these two major programming concepts differ based on different parameters. And later in the article, we will take some examples to understand these concepts better.
So, let’s start with the tabular difference between Recursion and Iteration.
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What is the Difference Between Recursion and Iteration?
| Recursion | Iteration | |
| Definition | A technique in which the function calls itself in its body to solve the problem, typically breaking into smaller and more manageable sub-problems. | Iteration is a technique that repetitively executes a code block until the condition is unmet. |
| Syntax | There is a termination condition specified. | The iteration format includes initialization, condition, and increment/decrement of a variable. |
| Control Structure | Function call stack | Looping Constructs (for, while etc.) |
| Problem-Solving Approach | Divide and Conquer | Sequential Execution |
| Time Complexity | Higher due to the overhead of maintaining the function call stack. | Lower than recursion due to the absence of the overhead of function calls. |
| Space Complexity | Higher than iteration. | Generally lower than recursion due to the absence of the overhead function calls. |
| Memory | Uses more memory | Uses less memory |
| Speed | Slower than Iteration | Faster than Recursion as it uses less memory |
| Application | For Functions | For Loops |
| Usage | Tree/Graph Traversal or the problem that can be broken down into similar sub-problems | Preferred when tasks require repetition of similar tasks over elements in a structure (example, list). |
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What is Recursion?
Recursion in programming is a method where the solution to a problem depends on solutions to smaller instances of the same problem. Essentially, a recursive function is a function that calls itself during its execution. This enables the function to be repeated several times, as it can call itself during its execution.
Now, let’s have a look at some examples to get a better idea of recursion.
Examples of Recursion
Ques-1: Calculate Fibonacci Series
def fibonacci(n): # Base case if n <= 1: return n # Recursive case else: return fibonacci(n-1) + fibonacci(n-2)
# Testingprint(fibonacci(10))
Ques-2: Tower of Hanoi
def hanoi(n, source, target, auxiliary): if n > 0: # Move n - 1 disks from source to auxiliary, so they are out of the way hanoi(n - 1, source, auxiliary, target)
# Move the nth disk from source to target print('Move disk', n, 'from', source, 'to', target)
# Move the n - 1 disks that we left on auxiliary to target hanoi(n - 1, auxiliary, target, source)
# Testinghanoi(3, 'A', 'C', 'B')
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What is Iteration?
Iteration in programming is a process wherein a set of instructions or structures are repeatedly executed until some condition is met. We often use loops for iteration in Python, such as the for and while loops.
Now, let’s have a look at some examples to get a better idea of iteration.
Example of Iteration
Ques-1: Find all Prime Number up to a given number.
def primes_up_to(n): """ Function to calculate all prime numbers up to a given number. :param n: the upper limit number :return: a list of prime numbers """ primes = [] for potential_prime in range(2, n): is_prime = True for num in range(2, potential_prime): if potential_prime % num == 0: is_prime = False if is_prime: primes.append(potential_prime) return primes
print(primes_up_to(100))
Ques-2: Calculate the Factorial of a given number.
def factorial(n): """ Function to calculate the factorial of a given number. :param n: the input number :return: factorial of the input number """ result = 1 for i in range(1, n+1): result *= i return result
print(factorial(5))
Ques-3: Find all the occurrence of a substring in a string?
def find_substring(string, substring): """ Function to find all occurrences of a substring in a string. :param string: the input string :param substring: the substring to be found :return: a list of indexes where the substring starts in the string """ indexes = [] index = string.find(substring) while index != -1: indexes.append(index) index = string.find(substring, index + 1) return indexes
print(find_substring('This is a test. This is only a test.', 'test'))
Key Differences Between Recursion and Iteration?
- Recursion is a technique in which the function calls itself in its body to solve the problem, typically breaking into smaller and more manageable sub-problems. In contrast, Iteration is a technique that repetitively executes a code block until the condition is unmet.
- Recursion follows the divide and conquers approach, while Iteration follows the sequential execution approach to solve the problem.
- The time complexity of recursion is higher than Iteration due to the overhead of maintaining the function call stack.
- Iteration is faster than recursion due to less memory usage.
- Iteration is preferred for loops, while recursion is used for functions.
Conclusion
Recursion and Iteration are two important concepts of programming where we need to repetitively do certain operations until the given condition is not met. In this article, we have briefly discussed what is Recursion, what is Iteration with the help of examples and later in the we have also discussed the key differences between recursion and iteration.
Hope you will like the article.
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FAQs
What is Recursion?
Recursion in programming is a method where the solution to a problem depends on solutions to smaller instances of the same problem. Essentially, a recursive function is a function that calls itself during its execution. This enables the function to be repeated several times, as it can call itself during its execution.
What is Iteration?
Iteration in programming is a process wherein a set of instructions or structures are repeatedly executed until some condition is met. We often use loops for iteration in Python, such as for and while loops.
What are the key differences and similarities between recursion and iteration?
Recursion is a technique in which the function calls itself in its body to solve the problem, typically breaking into smaller and more manageable sub-problems. In contrast, Iteration is a technique that repetitively executes a code block until the condition is unmet. Recursion follows the divide and conquers approach, while Iteration follows the sequential execution approach to solve the problem. The time complexity of recursion is higher than Iteration due to the overhead of maintaining the function call stack. Iteration is faster than recursion due to less memory usage. Iteration is preferred for loops, while recursion is used for functions.
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