# Monthly Archives: October 2021

# Array Fun 2 [2021]

Complete all the methods below. When you are done, copy and paste the testmethods.v4 into your class and run it to see if you have any obvious errors.

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

Description:This method returns the sum of every`n`

elements of`num`

s..

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) |

**String[] doubleArr(String[] strs)**

Description:This method returns a new version of`strs`

in which each element now appears twice. This can be done with a for-each loop, which I believe is easier and more intuitive.

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”} |

**int indexOf5(int[] nums )**

Description:This returns the index of the first occurrence element 5 or -1 if 5 does not appear anywhere in the array.

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 |

More Sample calls and return vals

**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 |

**int[] randos(int start, int end, int howMany)**

Description:This method returns an array of random numbers between [start,end] . Note make sure that each element in the new array attempts to make a new random int.

**double meanBetween(int[] nums, int min, int max)**

Description:This method returns the mean of nums ; however, this method only counts values within the range (min,max) as shown in the examples below:

**int secondSmallest(int[] nums )**

Description:This method returns the element of`nums`

with the second smallest value.Note: You may not modify the input array. For instance, you may not put nums in order, which would be bad because you were not asked to modify the array.

@precondition: nums.length >= 2

Note: You will lose credit if you use a constant to represent the smallest or second smallest number. See pseudocode

Method Call |
return value/output |

secondSmallest( { 2 , 18 , 22, 4 , 6 } ) | 4 |

secondSmallest( { 3 , 7 , 15 , 1 ,101} ) | 3 |

**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 10110_{2}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.Ifthe number of digits in thesum exceeds the maximum number of digits (5) , you should throw an arithmetic exception as shown in the code below:

12 if(overFlowAdditionOccurred)throw new ArithmeticException("Addition Overflow Error");

**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 ( 11_{2} + 1_{2}= 100_{2} ) |

Old versions:

# String 1 and Array 1 Exercises

Exercises for String 1 and Array 1 (no loops)

When you are done, you can copy and past the score() method below into your class. It will test some (but, *by no means* all) of the things that your code should do

Create a class called StrArr1 and add each method below into it.

For the absVals() method below use the Math.abs() Java method.

For the randos1to10() method below use the Math.random() Java method. Create a new array to store random integers. Each integer should be [1,10]