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74 lines
No EOL
1.3 KiB
Markdown
74 lines
No EOL
1.3 KiB
Markdown
# Lecture for February 13
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## Loops
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###Why Loops?
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While some check is true, repeat the work.
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While the cookies aren't baked, keep baking
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### Loop Building Process
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1. Identify one test that must be true when the loop is finished
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2. Use the **opposite** form of the test
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3. Within loop, make *progress* towards completion of the goal.
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### While syntax
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```java
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while (expression) {
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// Loop body executes if expression is true
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}
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// Statements execute after expression is false
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```
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### Getting Input (Songs in a Playlist Psuedocode)
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```java
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// Ask user about first song
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while (user says play next song) {
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// play next song
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// ask user about next song
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}
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```
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### Nested Loops
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You can have loops inside loops
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```java
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int outer = 1;
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while (outer < 4) {
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int inner = 1;
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while (inner < 4) {
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System.out.println(outer + ":" + inner);
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inner++;
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}
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outer++;
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}
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```
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This code does the following
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```reStructuredText
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1:1
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1:2
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1:3
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2:1
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2:2
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2:3
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3:1
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3:2
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3:3
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```
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### Break Down the Problem
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Never write the entire program at once! This makes it incredibly hard to debug. Instead break it into small parts.
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Write one part -> debug until it works
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Write second part -> debug until it works
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This way you know which part of your code failed, instead of having everything fail. |