Transcript 5. function2x

5. Function (2)
and Exercises
Minhaeng Lee
Random Number
• Generate random number between 0 to 1.0
– Math.random();
• Generate random number between 0 to N
– (int)(Math.random() * N);
• Exercise: Try to print 10 times of randomly
generated numbers using loop statement
Exercise : coin gambling
• Make function that return true/false
• Inside of the function, do random between 0
to 1, if the value is less than 0.5 then return
true, otherwise return false
• Run 1000 times, then count true and false
Factorial
• Factorial
– N! = N*(N-1)*(N-2)*…
• Define function
• Exercise : Using loop statement
Recursion of recursive call
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Call function itself
Need termination phrase
Sometimes very convenient
Not memory efficient
Recursion Example : Factorial
Recursion Exercise : Fibonacci
Wikipedia.org
Write Fibonacci
• Iterative way
• Recursive Way
Function Overloading
• To make functions Same name but different
body
• Why?
– Sometimes, we need make multiple functions have
similar name for program simplicity
– Example : add functions using integer input and String
inputs. They should have similar name but different
body to process different inputs
• For overloading, at least one of parameters must
be different to the others
Overloading. When do we need?
They have similar function name but parameter types are different.
Overloading Example
They MUST have at least one parameter which has different TYPE (not name)
Because a function is distinguished with function name and parameter types.
Useful library Vector
• Array has size limit (defined at the first time)
• But sometimes, we cannot expect its
optimized size
• By using Vector, we don’t have to think about
it
• Vector<Type> <variable Name> = new Vector<Type>();
Vector Example
Type it and see how it works
Vector Example
Type specified
Type it and see how it works
Type cannot be primitive types. Use Integer instead of int, Double instead of double,
Float instead of float
Exercise: Big number calculator
Exercise: Big number calculator
• How can we store a number over the memory
size of variable types?
– We knows the upper-bound of variables
• Store each digit of input number as individual
letter
• Then compute add, minus, multi, divide as
we’ve learned in elementary school
Big number calculator
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Big number calculator
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Big number calculator
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Big number calculator
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Carry
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Big number calculator
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Big number calculator
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Big number calculator
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Big number calculator
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Exercise Time!
• Write Big Number Calculator for bigAdd
• Use this template
– https://github.com/mhlee1215/java_class/blob/master/CodingExercise/src/Bi
gNumberCalculatorTemp.java
• Reverse ordering makes it easy to compute
– Because human being and machine have different order of numbers
– Human being: right to left
– Machine: left to right
Homework
• Step1. Complete bigSub
• Step2. Complete {bigMul or bigDiv}
• Integrate with interactive calculator