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Lecture 18Lecture 18Version 1.0Version 1.0

RecursionRecursion

2Rushdi Shams, Dept of CSE, KUET, Bangladesh

What is RecursionWhat is Recursion

A function is called ‘recursive’ if a A function is called ‘recursive’ if a statement within the body of a statement within the body of a function calls the same function function calls the same function

Sometimes called ‘circular Sometimes called ‘circular definition’ definition’


IterationIteration


RecursionRecursion


ExplanationExplanation


More Simpler RecursionMore Simpler Recursion


And the classical And the classical problemproblem


Iteration vs RecursionIteration vs Recursion 1. Both iteration and recursion are based on 1. Both iteration and recursion are based on

control structure. Iteration uses a repitation control structure. Iteration uses a repitation structure and recursion uses a selection structure and recursion uses a selection structure.structure.

2. Both involves in a termination state checking. 2. Both involves in a termination state checking. 3. Both can be run infinitely. (which is of course 3. Both can be run infinitely. (which is of course

not desirable)not desirable) 4. Recursion is expensive in case of memory and 4. Recursion is expensive in case of memory and

processing time than iteration.processing time than iteration. 5. Recursion for many cases makes programs 5. Recursion for many cases makes programs

easier.easier. 6. Recursion is the style of stylish programmer. 6. Recursion is the style of stylish programmer.

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