Monthly Archives: April 2014

Array Fun 1 [Java]

Array Fun 1

 

Create a Class called ArrayFun that has the following methods Write the body for the methods described below.

public int[] swapFirstLast(int[] nums)

Description: This method returns a new version of the array with the first and last elements ofnums swapped.

Method Call return value/output
swapFirstLast( {3, 2 ,5 } ) {5,2,3}
swapFirstLast( {7, 6 ,9 ,12} ) { 12 , 6 , 9, 7}

public String[] swapFirstMiddle(String[] strs)

Description: This method returns a new version of the array with the first and middle elements ofstrs swapped.

Method Call return value/output
swapFirstMiddle( {“a”,”b”,”c” } ) { “b”, “a”, “c”}
swapFirstMiddle( { “zoo”,”foo”, “xoo”} ) { “foo”,”zoo”, “xoo”}

Loops


public void printEveryOther(int[] nums)

Description: This method prints every other element of nums on new lines .

Method Call return value/output
printEveryOther( {1 , 2 , 3 , 4 } ) 1
3
printEveryOther( {13 , 42 , 33 , 44 , 52} ) 13
33
52

public int sum(int[] nums )

Description: This method returns the sum of nums..

Method Call return value/output
sum( { 2 , 8 }) 10 ie 2 + 8
sum( { 2 , 8 , 4 } ) 14 ie (2 + 8 + 4 )

public int sumOdds(int[] nums )

Description: This method returns the sum of all the odd element of nums.

Method Call return value/output
sumOdds( { 5 , 2, 4 , 6 , 7 } ) 12 ( ie 5 + 7 )
sumOdds( { 13 , 3, 2, 6 , 7 } ) 23
public double mean(int[] nums )

Description: This method returns the mean of nums. Pay close attention to the second sample call and make sure you get “5.25

Method Call return value/output
mean( { 2 , 8 }) 5.0 ie (2+8)/2
mean( { 2 , 8 , 4 , 7 } ) 5.25 ie (2+8+4+7)/4

public double largest(double[] nums )

Description: This method returns the element of nums with the greatest value. Make sure that you test out the second call and get ‘-2‘.

Method Call return value/output
largest( { 2.6 , 8.2, 5.2}) 8.2
largest( { -2,-11, -4} ) -2

public int sumEveryN(int[] nums, int n)

Description: This method returns the sum of every n elements of nums..

Method Call return value/output
sumEveryN( {1 , 2 , 3 , 4 }, 2 ) 4( ie 1 +3)
sumEveryN( {13 , 42, 15, 33 , 44 , 16 , 52} ,3) 98 ( ie 13 + 33+ 52)

*public int secondSmallest(int[] nums )

Description: This method returns the element of nums with the second smallest value.

Method Call return value/output
secondSmallest( { 2 , 18 , 22, 4 , 6 } ) 4
secondSmallest( { 3 , 7 , 15 , 1 ,101} ) 3

** boolean isPalindromic(int[] nums)

Description:This method returns true if the elements of nums are a palindrome..

Method Call return value/output
isPalindromic(( { 5 , 2, 7 , 2 , 5} ) true
isPalindromic( { 5 , 2, 7 , 3 , 5} )) false
isPalindromic(( { 1 , 2, 1} ) true

 


 The question below is extra credit .
** int[] add(int[] num1, int[] num2, int base) throws ArithmeticException
@precondition 1 < base < 11
@precondition num1.length = 5 and num2.length = 5
@postcondition: the returned array has 5 elements representing the sum or an ArithmeticException is thrown

Description: This method attempts to replicate addition. Consider both num1 and num2 represent the five digits of a number. Each element in the array stores one of the digits. For instance, the number 143 would be represented as {0,0,1,4,3 }. Numbers can be in any base between 2 and 10 inclusive , and the number 101102 in binary would appear in an arrays as : {1, 0, 1 , 1, 0 } . Let’s assume the numbers are positive. You should return an array representing the digits of the sum of num1 and num2.  You may not do any math besides addition. You may not use any external libraries for any math or base conversions.   If the number of digits in the sum exceeds the maximum number of digits (5) , you should throw an arithmetic exception as shown in the code below:

Note: You may not use any kind of helper or utility methods that are built into pre-defined Java classes for converting numbers between bases. Only use techniques taught in this class.  What you have to do is reproduce the additional algorithm and find a way to carry digits , programmatically.

Method Call return value/output
add( {0,0,0 ,4,2},{0,0,0,5,1}, 10) {0, 0, 0, 9, 3} ie (42 + 51 = 93)
add( {0, 0, 0 ,7,2},{0,0,0,5,1}, 10) {0, 0 , 1 , 2, 3} ie (72 + 51 = 123)
add( {0, 0 , 0 , 1 , 1}, { 0 , 0 , 0 , 1 }, 2) {0, 0 , 1 , 0 , 0} ie ( 112 + 12= 1002 )