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Warm-up 8/27

Please place your name tag on your table.
Open Repl.it - be ready to share your Unicode program

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Nerves by DPR IAN - Leisha

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2

Repl.it 01-04.exploreUnicode

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Recursion occurs when a method calls itself.

A recursive method must have a stop condition or base case. Recursive calls will continue until the stop condition is met.

Recursion

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Recursion occurs when a method calls itself.

Be ready to answer the following questions after watching the video:

1. What is the first thing you have to "get happy about" when making recursive calls according to Professor Brailsford?

2. What solves this problem that Professor Brailsford describes?

Computerphile (begin at 4:00)

Recursion and the call stack

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During the method execution the code can only access the values in the current (i.e. top-most) stack frame.�

This way a single (local) variable can seemingly have many different values at the same time (as when a recursive method calls itself multiple times).

The Stack

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SF1- method() call

The Stack

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SF1- method() call

SF2- method() call

The Stack

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SF1- method() call

SF2- method() call

SF3- method() call

The Stack

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SF1- method() call

SF2- method() call

SF3- method() call

SF4- method() call

The Stack

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SF1- method() call

SF2- method() call

SF3- method() call

The Stack

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SF1- method() call

SF2- method() call

The Stack

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SF1- method() call

The Stack

As each call to the method completes, the instance of that method is removed from the stack.

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13

Repl.it 01-05.Cat in the Hat - recursion 2

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Repl.it 01-05.Cat in the Hat - recursion 3

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Write implementations using:

computation

public int bunnyEars2(int bunnies)

{

return 2 * bunnies + (bunnies/2);

}

CodingBat: bunnyEars2

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Write implementations using:

b) iterative

int output = 0;

for (int i = 1; i <= bunnies; i++)

{

if (i%2 == 0)

{

output += 3;

}

else

{

output+= 2;

}

return output;

CodingBat: bunnyEars2

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Write implementations using:

c) recursion

if (bunnies == 0)

{

return 0;

}

else if (bunnies % 2 ==0)

{

return 3 + bunnyEars2(bunnies-1);

}

else

{

return 2 + bunnyEars2(bunnies-1);

}

CodingBat: bunnyEars2

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Share solutions.

a) iterative

CodingBat: fibonacci

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Share solutions.

b) recursive

CodingBat: fibonacci

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Repl.it: Fibonacci - recursively

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Repl.it 01-06 Cat in the Hat - recursion 3
Repl.it 01-07 Fibonacci - recursively
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