Tag Archives: arrays

Array Fun 2

Array Fun 2

Java Assignment

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

 

public int[] digitsToArray(int nums)

Description: This method creates an array that is filled with all of the digits of nums.

Method Call return value/output
digitsToArray( 523 ) {5,2,3}
digitsToArray(1267 ) { 1 , 2 , 6 , 7}
public boolean allFactorsOfSum(int[] nums)

Description: This method returns true if each element ofnums is a factor of the sum of nums.

Method Call return value/output
allFactorsOfSum( {6,1,2,3} ) true (because all of the elements are factors of the sum which is12)
allFactorsOfSum( 1,4,7) false (because 7 is not a factor of the sum of this array which is 12)
public String[] doubleArr(String[] strs)

Description: This method returns a new version of strs with each element appearing twice.

Method Call return value/output
doubleArr( {“a”,”b”,”c”} ) {“a”,”a”,”b”,”b”, “c” , “c”}
doubleArr( {“math”,”ware”,”house”,”.com” }) {“math”,”math”,”ware”,”ware”,”house”,”house”,”.com”, “.com”}
public boolean isThere(int[] nums, int num)

Description: This method returns true if num is an element nums.

Method Call return value/output
isThere( {6,1,2,3}, 6) true
isThere( {6,1,2,3}, 5 ) false
public int indexOf(int[] nums, int num)

Description: This method returns the index value of the first appearance of num or -1 if num is not an element of nums .

Method Call return value/output
indexOf( {6,4 ,7,3, 4 }, 4) 1
indexOf( {6,4 7 ,3,2,7}, 7) 2
indexOf( {6,4 ,2,3}, 22) -1
public int lastIndexOf(int[] nums, int num)

Description: This method returns the index value of the last appearance of num or -1 if num is not an element of nums .

Method Call return value/output
lastIndexOf( {6, 4 ,7 ,3, 11, ,4}, 4) 5
lastIndexOf( {7, 6,4 , 7 ,3}, 7) 3
lastIndexOf( {6,4 ,2,3}, 22) -1
public boolean isIncreasing(double[] nums)

Description: This method returns true if each element in nums is greater than the element to its left.

Method Call return value/output
isIncreasing( {1,2,3,4 }) true
isIncreasing( {1,0 ,3,4 }) false
isIncreasing( {1,1, 2,3,4 }) false
public int largestSpan(int[] nums)

Description: This method returns the largest span of consecutive increasing numbers

Method Call return value/output
largestSpan( {4, 3, 1, 2, 3 , 1} ) 3
largestSpan( {4  , 3,  1 , 12 , 31 , 44 , 52 , 1} ) 5
largestSpan( {9, 7, 8 , 12,4, 3, 0, 4 , 1) 3
largestSpan( {1, 0, 4, 5 , 3,  2, 8 , 9, 10, 12, 4, 3,  1 }) 5
** int[] invert(int[] nums)

Description: This method ‘inverts’ an array by spliting the array in halves and ‘inverting’ each half. See sample calls to understand.

Method Call return value/output
invert( {5 , 21, 5, 13,4 }) {4, 13, 5, 21, 5  }
invert( { 1, 2, 3, 4, 5,6  })  { 6, 5, 4, 3, 2, 1}
** int[] shiftByN(int[] nums, int delta)

Description: This method returns the array with all digits shifted by delta . Any digits that are circulated off the end of the array should be returned to the other side. Note: delta could be positive or negative. Please keep in mind that Math.abs(delta) > nums.length could be possible 😉

Method Call return value/output
shiftByN( {5 , 21, 13,4 } 1) { 4 , 5 , 21, 13 }
shiftByN( {5 , 21, 13, 4 , 11} 2) { 4 , 11 , 5 , 21, 13}
shiftByN( {5 , 21, 13, 4 } -1) { 21, 13, 4 , 5}
shiftByN( {5 , 21, 13, 4 ,7 } -2) { 13, 4 ,7 , 5 , 21}
** 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. 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.

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 )

Array Fun 2 [Java]

public int[] digitsToArray(int nums)

Description: This method creates an array that is filled with all of the digits of nums.

Method Call return value/output
digitsToArray( 523 ) {5,2,3}
digitsToArray(1267 ) { 1 , 2 , 6 , 7}
public boolean allFactorsOfSum(int[] nums)

Description: This method returns true if each element of nums is a factor of the sum of nums.

Method Call return value/output
allFactorsOfSum( {6,1,2,3} ) true (because all of the elements are factors of the sum which is12)
allFactorsOfSum( {1,4,7 }) false (because 7 is not a factor of the sum of this array which is 12)
public String[] doubleArr(String[] strs)

Description: This method returns a new version of strs with each element appearing twice.

Method Call return value/output
doubleArr( {“a”,”b”,”c”} ) {“a”,”a”,”b”,”b”, “c” , “c”}
doubleArr( {“math”,”ware”,”house”,”.com” }) {“math”,”math”,”ware”,”ware”,”house”,”house”,”.com”, “.com”}
public boolean isThere(int[] nums, int num)

Description: This method returns true if num is an element nums.

Method Call return value/output
isThere( {6,1,2,3}, 6) true
isThere( {6,1,2,3}, 5 ) false
public int  indexOf5(int[] nums )

Description: This returns the index of the first occurrence element ‘5’ or -1 if 5 does not exist.

Method Call return value/output
indexOf5( { 2 , 3 , 5 , 4 } ) 2
indexOf5( { 2 , 3 , 5 , 4, 5  } ) 2
indexOf5( { 2 , 3 ,7  , 4, 3,   } ) -1

 

public int indexOf(int[] nums, int num)

Description: This method returns the index value of the first appearance of num or -1 if num is not an element of nums .

Method Call return value/output
indexOf( {6,4 ,7,3, 4 }, 4) 1
indexOf( {6,4 7 ,3,2,7}, 7) 2
indexOf( {6,4 ,2,3}, 22) -1
public int lastIndexOf(int[] nums, int num)

Description: This method returns the index value of the last appearance of num or -1 if num is not an element of nums .

Method Call return value/output
lastIndexOf( {6, 4 ,7 ,3, 11, ,4}, 4) 5
lastIndexOf( {7, 6,4 , 7 ,3}, 7) 3
lastIndexOf( {6,4 ,2,3}, 22) -1
public boolean isIncreasing(double[] nums)

Description: This method returns true if each element in nums is greater than the element to its left.

Method Call return value/output
isIncreasing( {1,2,3,4 }) true
isIncreasing( {1,0 ,3,4 }) false
isIncreasing( {1,1, 2,3,4 }) false
 isIncreasing( {-1, –1, -2, -3, -4 })  false
* public int largestSpan(int[] nums)

Description: This method returns the largest span of consecutive increasing numbers

Method Call return value/output
largestSpan( {4, 3, 1, 3, 6 , 1} ) 3
largestSpan( {4 3 1 , 12 , 31 , 44 , 52 , 1} ) 5
largestSpan( {1 , 7 8 , 12,4, 3, 0, 4 , 1) 3
** int[] invert(int[] nums)

Description: This method ‘inverts’ an array by spliting the array in halves and ‘inverting’ each half. See sample calls to understand.

Method Call return value/output
invert( {5 , 21, 5, 13,4 }) {21 , 5 , 5, 4,13 }
** int[] shiftByN(int[] nums, int delta)

Description: This method returns the array with all digits shifted by delta . Any digits that are circulated off the end of the array should be returned to the other side. Note: delta could be positive or negative. Please keep in mind that Math.abs(delta) > nums.length could be possible 😉

Method Call return value/output
shiftByN( {5 , 21, 13,4 } 1) { 4 , 5 , 21, 13 }
shiftByN( {5 , 21, 13, 4 , 11} 2) { 4 , 11 , 5 , 21, 13}
shiftByN( {5 , 21, 13, 4 } -1) { 21, 13, 4 , 5}
shiftByN( {5 , 21, 13, 4 ,7 } -2) { 13, 4 ,7 , 5 , 21}
*** 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. 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.

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 )

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

2 D Arrays in Java Assignments

Add the following Methods to a class called ArrayFun2D

public void print(int[][] arr)

Description: This method prints each element in the array. This will be a useful method when you are debugging your code and want to test it out to see if it works.

Method Call return value
print({{1,2} , {3,4}, { 5, 6 } } ) 1   2
3  4
5   6

public int sum(int[][] arr)

Description: This method returns the sum of all elements in the array

Method Call return value
sum({{1,2} , {3,4}, { 5, 6 } } ) 21 ( ie 1+2+3+4+5+6)

public String concat(String[][] strs)

Description: This method returns the concatenation of all the elements in the Array

Method Call return value
concat({{“a”,”xc” }, {“t”, “zoo”}, { “jjkj” } } ) “axctzzoojjkj”

public double mean( int[][] arr)

Description: This method returns the arithmetic mean of the array. Make sure you double check that you are correctly returning results that include decimal values .

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

public void printRow(int[][] arr, int row)

Description: This method prints all elements in rowThis can be (and should be) done with a single loop.

Method Call return value
printRow({{1,2} , {3,4}, { 5, 6 } } , 1 ) 3, 4
printRow( { 5 , 6} , {7, 12, 13 , 5 }, { 5, 6 ,0} } , 2 ) 5 , 6, 0

public void printCol(int[][] arr, int col)

Description: This method prints all elements in col

Method Call return value
printCol({{1,2} , {3, 4}, { 5, 6 } } , 1 ) 2
4
6
printCol( { 5 , 6} , {7, 12, 13 , 5 }, { 12, 6 ,0} } , 0 ) 5
7
12
printCol(    {12, 13 , 5 }, { 6, 2, 13 ,11}  , {1,2 } } , 2 ) 5
13

public int maxVal_inRow(int[][] arr, int row)

Description: This method returns the value of the largest number in the given row

Method Call return value
maxVal_inRow({{1,2} , {3,4}, { 5, 6 } } , 1 ) 4
maxVal_inRow ({   { 5 , 6} , {7, 12, 13 , 5 }, { 5, 6 ,0} } , 2 ) 6

public int maxVal_inCol(int[][] arr, int col)

Description: This method returns the value of the largest number in the given col

Method Call return value
maxVal_inCol({{1,2} , {3,4}, { 5, 6 } } , 0 ) 5
maxVal_inCol({{1,-2} , {3,-4}, { 5, -5 } } , 1 ) -2

public int[][] changeValues(int[][] table, int val)

Description:This method returns the array with all elements set toval

changeValues(table, 5)

Original Array

1 2
3 4
5 6
Returned Array

5 5
5 5
5 5

public void print_colMajor(int[][] arr)

Description: This method prints each element in the array – using column major order

Method Call return value
print({{1,2} , {3,4}, { 5, 6 } } ) 1   3   5
2  4    6

 

public int[][] removeVals(int[][] table, int val)

Description: This method returns a version of the 2-d array where val has been removed from all elements

removeValues(table, 5)

Original Array

{1 , 5}
{3, 4}
{5, 6}
Returned Array

{1}
{3, 4}
{6}

 

int[] twoD_to1D(int[][] arr)

Description: This method takes an input array that is in 2 dimensions  and  creates a 1 d array . Assume that the array is rectangular (not jagged).

Method Call return value
twoD_to1D ( {{1,2} , {3,4}, { 5, 6 } } ) { 1 , 2 ,  3 ,  4 , 5 ,  6 }

Matrices

int[][] add (int[][] matr1, int[][] matr2)

Description: This method returns the sum of matr1 and matr2

how to add matrices


 

** int[][] multiply(int[][] matr1, int[][] matr2)

Description: This method returns the product of matr1 and matr2

how to multiply matrices

**public int[][] invertValues(int[][] matr)

Description: This method returns the paramater with its values ‘inverted’

Original Array

1 2
3 4
5 6
Returned Array

6 5
4 3
2 1

Extra Credit Java Arrays Question

Extra Credit (GOOD LUCK!)

 

Note first try addition , also worth some (though less) extra credit.

** int[] multiply(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 product or an ArithmeticException is thrown

Description: This method attempts to replicate multiplication. Both num1 and num2 represent five digit numbers. 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 product of num1 and num2. If the number of digits in the product 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.

Method Call return value/output
multiply ( {0,0,0 , 4,2},{0,0,0,5,1}, 10)   {0 , 2 ,  1 ,  4 ,  2}    (42 *51= 2142)
multiply ( {0,0,0, 3,1} , { 0 ,0,0,2,4}, 10) {0 , 0 ,  7 , 4 ,  4}    (31 *24= 744)
multiply ( {6,5,1, 3,1} , { 0 ,0,0,2,4}, 10) throw an ArithmeticException

Tool for checking work

Use programmers calc to check your work. This is an awesome 64 calculator and you can multiply in binary, decimal or octal to help you see if you did your work correctly.