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Author Archives: Mr. M
Java Strings -Introduction
Java Strings
Learning Goals
- How do we make Strings and how do they work in memory?
- How do we perform common operations with Strings?
Assignments Goals
Java Strings
Java Strings
- Strings in Java
- String Assignments #1
- String Loops Review (word doc)
-
- Strings Assignments This should be too easy for anyone who took the Java course so skip these if they are too easy for you
- Looping over String Projects
- String Loops 1
- String Loops 2 (must do) Due:EOD Tuesday 10/22
- String Projects #1 do the (Validate User Input Project)
- testcases_validate_form
- Required Coding Bat Problems
- Some Practice Problems
-
climb-the-stairs-[python]
Climb The Stairs
For all these maps:
- Start your jeroo in the bottom left , at 23,0
- use 1 and only 1 while loop
- you may only hop() 1 space at a time
- pick the flower at the end.
climb-the-stairs__1.jev
climb-the-stairs__2.jev
climb-the-stairs__3.jev
climb-the-stairs__4.jev
climb-the-stairs__5.jev
climb-the-stairs__6.jev
climb-the-stairs__7.jev (GRADE BOOK)
climb-the-stairs__8.jev (GRADE BOOK)
climb-the-stairs__9.jev
**( Only if you want to get that ‘A’)
Pascal’s Triangle Recursion example
Pascal’s Triangle
Pascals Triangle presents a simple formula for expanding binomials. If you think a little bit about how Pascal’s Triangle determines each term, you should see that a recursive method is used!
The animation below demonstrates the recursive nature of Pascal’s Triangle.
Part I
Objective: to employ recursion to be able to print out an entire line of Pascal’s Triangle . Look at the animation, getting a particular term in a line is inherently recursive. This class should throw an ArithmeticException if you attempt to calculate an invalid Term. (quick example of how to throw an Exception)
Hint: You only need to use recusion to get the term of the expansion.
Part II
Now that you can print out an entire line of Pascal’s Triangle. Print out the entire triangle up to some degree ‘n’.
java-recursion-excercises-1
void countDown(int num)
Description: This method prints the numbers from num down to and including on new lines
| Method Call | output |
| countDown(5) | 5 4 3 2 1 0 |
| countDown(3) | 3 2 1 0 |
void printRev(String s)
Description: This method prints each letter of String s on new lines in reverse order.
| Method Call | output |
| printRev(“abcdef”) | a b c d e f |
| printRev(“abc”) | a b c |
int sumLessthan(int n)
Description: This method returns the sum of all positive integers less than or equal to n
| Method Call | output |
| sumLessThan(4) | 10 (4+3+2+1) |
| sumLessThan( 5 ) | 15 ( 5 + 4 + 3 + 2 + 1) |
int sumLessthan(int n)
Description: This method returns the sum of all positive integers less than or equal to n
| Method Call | output |
| sumLessThan(4) | 10 (4+3+2+1) |
| sumLessThan( 5 ) | 15 ( 5 + 4 + 3 + 2 + 1) |
double average( int[] nums, int index)
Description: This method returns the average of all the elements in nums. The parameter ‘idnex’ is used to keep track of how far along you have gone in the array.
| Method Call | output |
| average({3,2,1}, 0) | 2 |
| average({3,2,2}, 0) | 2.333333 |
Recursion in Java
Recur
- What happens, when you Google recursion?
- First : go to and read this page
- Download and run this code
- Complete these excercises in BlueJ
- Coding bat excercises
bunnyEars2() (try to figure out what goes where the question marks are)
|
1 2 3 4 5 6 |
if(bunnies == 0) return 0; if(bunnies % 2 == 0) return 3 +bunnyEars2(?????); return 2 +bunnyEars2( ????? ); |
Recursion problems (bunny ears is a good, straight forward one to start with)
- fibonacci()
- countHi()
- then try sumDigits()
- array6()
- array220()
- powerN()
- countHi()
- ** http://codingbat.com/prob/p195413
- ** http://codingbat.com/prob/p118182
- any of the last 6 problems
- ** print Pascal’s Triangle. Use recursion and no loops
Jeroo in Python — while loop vs if test
Two Friends Meet
Two Friends Meet
- Create two different Jeroos
- one Jeroo should start at (0,0) and be facing EAST
- the other should start at (0,23) and be facing west
- they should move at “the same time” and plant flowers in the pattern shown below
- use a single while loop
- the isJeroo( relative_diretion) method might be helpful
- Note: To get 100%
- Your loop MUST end (not infinite)
- You can not use hasFlower()
Traversing the Rim
In the prior assignment (#2b), you were asked to go around the inner lake as shown below. We are going to add 1 new requirement to this
- with a flower in 6,6
- using while loop(s) traverse around the border of the inner lake
- For each map, you should pick the flower, after the loop is over
What is new this time?
- You are forced to use 1 and only 1 while loop .
- you can only use hop() (ie you can’t hop more than 1 space)
- after the loop is done , then you can pick() the flower
recangular-lake.jev
recangular-lake-if2.jev
Scroll down for a hint about how to handle if test #1 for this map.
A closerlook at if test #1 (how to get around that first if test)
rectangular-lake-bumps1.jev
recangular-lake-bump3A.jev
recangular-lake-bump3B.jev ( NOT BEING GRADED, SKIP THIS)
walk-the-lake-jacks-map.jev
Write an infinite loop (1 while loop). You may NOT use isWater()
