12recursive_func

# 12recursive_func - Introduction to Computers and...

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Introduction to Computers and Programming Lecture 12 Prof. I. K. Lundqvist Reading: B pp. 181-189, FK pp. 591-621, handout Oct 1 2003 PRS 1 -- Scope 1. Nothing is displayed on the screen 2. 0 (zero) is displayed on the screen 3. 7 is displayed on the screen 4. Don’t know

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Recursion call themselves base case) is reached that can be solved immediately General algorithm if stopping condition then solve simple problem else use recursion to solve smaller problem(s) combine solutions from smaller problem(s) • Writing procedures and functions which •Invo lves – Solving large problems – By breaking them into smaller problems –Of ident ica l form • Eventually, a “trivial” problem (the •I tera t ion –Cogn it ive s imp le •Recurs – Is not as intuitive – Demanding on machine time and memory – Sometimes simpler than iteration
Guess a number Problem : think of a number in the range 1 to N Reworded : guess again Recursion comes into the “ guess again stage Factorial n , computes n! n! = 1 2 ... ( n -1) n 5! = 1 2 3 4 5 = 120 Receive: n , an integer Precondition: n >= 0 (0! = 1 and 1! = 1) Return: n! Given a set of N possible numbers to choose from Guess a number from the set –I f w rong , Continue until the number is guessed successfully A set of N-1 numbers remains from which to guess This is a smaller version of the same problem • Write a function that, given •Examp le: • Specification:

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Preliminary Analysis function return Positive is Result : Positive; begin Result := 1 ; for Count in 2 .. N loop
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12recursive_func - Introduction to Computers and...

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