ITI 1121 Lab 7 • Algorithms on Arrays solution


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Exercise 1: Execu8on 8me

• Recall a java method called linearSearch that we developed in class. It
takes as an input a reference to an array of integers and another integer,
called a key. The method returns an integer that is the first loca8on in the
array the key is found in, or -1 if the key is not found in the array.

• Then recall a java method called binarySearch that solves the same
problem but much more efficiently due to the fact that input is a sorted

• Open file. It contains both methods. In Speed. java you will see
first that we randomly generates an array, called numbers, of
SIZE=100,000 integers in the range [0 , 5*SIZE)
and a random integer, key, in range [0, 8*SIZE). Then we sort this array
using java.u8l.Arrays.sort(numbers).

Your job is to es8mate/observe/compare the execu8on 8mes of linearSearch
vs BinarySearch. ….. Con8nue to the next page

Exercise 1: Execu8on 8me
(Experiment) …con8nued

You can use the following code template to obtain the execu8on 8me in
nano seconds:
• long startTime = System.nanoTime();
• perfome the test
• long endTime = System.nanoTime();
• long execu8onTime = endTime – startTime;

Observe the difference in 8me taken by LinearSearch and BinarySearch. Play
with your code and try to do the same with an array of million integers, and
then with 10 million … etc. Observe the 8mes of execu8on.
Note however, that at some point your program will fail since the OS will not
be able to give you enough of memory (eg. for an array of size 100 million)

Exercise 2: Move Zeros Exercise

• Write a Java method that moves all the zeros in an
array to the end of the array. For example, if the
array is {1, 0, 3, 0, 0, 5, 7} the new array is {1, 3, 5, 7,
0, 0, 0}

• Program 2 different solu8ons:
– One should use a second, tmp, array to build the
result (easier problem).
– The other should be moving elements in the same
array without crea8ng any addi8onal arrays (so
called, in-place, solu8ons). (harder problem)
– For both problems the TAs will first discuss
algorithmic approaches to solve the problems.

Exercise 3:How do we make a method

return more than one value: – need to
put the values in an array and return the array
Implement a Java method that takes an array as
input, calculates the maximum and the minimum in
the given array, and returns as result and array with
two elements, the maximum value and the
minimum value.