1. Lecture 18
Version 1.0
Recursion

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
What is Recursion
 A function is called ‘recursive’ if a statement
within the body of a function calls the same
function
 Sometimes called ‘circular definition’

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
Iteration

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
Recursion

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
Explanation

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
More Simpler Recursion

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
And the classical problem

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Rushdi Shams, Dept of CSE, KUET,
Bangladesh
Iteration vs Recursion
 1. Both iteration and recursion are based on control
structure. Iteration uses a repitation structure and
recursion uses a selection structure.
 2. Both involves in a termination state checking.
 3. Both can be run infinitely. (which is of course not
desirable)
 4. Recursion is expensive in case of memory and
processing time than iteration.
 5. Recursion for many cases makes programs easier.
 6. Recursion is the style of stylish programmer. 