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Updated Readme with answers #33

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Updated Readme with answers #33

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52 changes: 26 additions & 26 deletions README.md
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Original file line number Diff line number Diff line change
@@ -1,15 +1,15 @@
# Recursion Problems

## Definitions
Define the following:
Define the following:

- Recursion
- Recursive Case
- Base Case
- Activation Chain/Stack
- Activation Record/Call
- Infinite Recursion/Stack Overflow/Stack too deep
- Tail Recursion
- Recursion - **The use of a method/application inside itself**
- Recursive Case - **A problem that is divided into smaller problems**
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This is not correct.

A recursive case is the case in which the method actually calls itself.

- Base Case - **An immediately solvable problem**
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i.e. Where the method knows the answer without recursing.

- Activation Chain/Stack - **All of the iterations of the method being called within itself**
- Activation Record/Call - **A single instance/iteration point of the method being called within itself**
- Infinite Recursion/Stack Overflow/Stack too deep - **An error that occurs when the method results in an infinite loop**
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I wouldn't say "error". It's a situation where the method results in an excessive use of memory that is usually caused by an infinite loop of sorts with many many calls to the recursive method.

- Tail Recursion - **A type of recursion where the recursive call is the very last function of the method/operation**

## Tracing through a recursive method

Expand All @@ -24,9 +24,9 @@ def mystery1(n)
end
```

- What is mystery1(5)?
- What is mystery1(10)?
- What is mystery1(0)?
- What is mystery1(5)? **15**
- What is mystery1(10)? **55**
- What is mystery1(0)? **Stack level too deep error**

### Trace #2
```
Expand All @@ -39,9 +39,9 @@ def mystery2(n)
end
```

- What is mystery2(123)?
- What is mystery2(9005)?
- What is mystery2(-123)?
- What is mystery2(123)?**6**
- What is mystery2(9005)? **14**
- What is mystery2(-123)?**-123**
- _Added Fun: How could we make `mystery2(-123)` work the way we might expect it to work instead of the way it does?_

### Trace #3
Expand All @@ -60,9 +60,9 @@ def mystery3(n)
end
```

- What is mystery3(1)?
- What is mystery3(13)?
- What is mystery3(-6)?
- What is mystery3(1)? **100**
- What is mystery3(13)? **100**
- What is mystery3(-6)? **200**

### Trace #4
```
Expand All @@ -75,9 +75,9 @@ def mystery4(b,e)
end
```

- What is mystery4(10,2)?
- What is mystery4(4,3)?
- What is mystery4(5,0)?
- What is mystery4(10,2)? **100**
- What is mystery4(4,3)? **64**
- What is mystery4(5,0)? **1**

### Trace #5
```
Expand All @@ -90,9 +90,9 @@ def mystery5(s)
end
```

- What is mystery5("hi")?
- What is mystery5("")?
- What is mystery5("Hi, there!")?
- What is mystery5("hi")? **
- What is mystery5("")? **blank**
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You should always put things that return a String in double quotes. For this answer, the answer should be "" (empty String) but saying "blank" is confusing.

- What is mystery5("Hi, there!")? ********** **(* 10 times)**
- _Added Fun: How could we make only alphabetic characters to be changed to stars?_

### Trace #6
Expand All @@ -110,7 +110,7 @@ def mystery6(s)
end
```

- What is mystery6("goodnight moon")?
- What is mystery6("Ada Developers Academy")?
- What is mystery6("Hi, there!")?
- What is mystery6("goodnight moon")? **moon goodnight**
- What is mystery6("Ada Developers Academy")?**Academy Developers Ada**
- What is mystery6("Hi, there **there! Hi,**
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Minor, but notable: there should be a leading space on each of these " moon goodnight", " Academy Developers Ada", " there! Hi,"

- _Added Fun: How could we make the reversal happen by letter, instead of by word (i.e. Make it so that mystery6("goodnight moon") returned "noom thgindoog")?_