CSE 214 Computer Science II (Spring 2015)

RECITATION 3 – Arrays

Objective:

1. To work with Arrays in Java.

2.  Analysis of code fragments

1.[20 min] Write a Java method that repeatedly selects and removes a random entry from an array until the array holds no more entries. link:http://www3.cs.stonybrook.edu/~sael/teaching/cse214/rec/RandomArray.java

[Note java.lang.Math.random() method is used to generate random numbers]

2. [20 min] Write the order of complexity for the following code fragments using Big O notation

(a) i=1;                      (b)                                         (c)

sum = 0;                         for (i=1; i<=n; i++)             for (i=1; i<=n; i++)

while (i <= n)               for (j=1; j<=i; j++)               for (j=1; j<=i; j++)

{                                                   X++                           for (k=1; k<=j; k++)

j=1;                                                                                        X++  

while (j <= n) {                                             

sum = sum + i;                             

j = j + 1;                                     

 }

i = i +1;                          

}

(i) Start off with a 2 dimensional array of equal width and height

(ii) Randomly populate this array with true’s and false’s. true’s represent live creates and false’s represent empty space.

(iii) Next, enter into an loop and evaluate the a cell after each generation

• Any live cell (true) with fewer than two live neighbours dies(caused by underpopulation).
• Any live cell (true) with more than three live neighbours dies, as if by overcrowding.
• Any live cell with two or three live neighbours lives, unchanged, to the next generation.
• Any dead cell with exactly three live neighbours cells will come to life.

Examples:

(a)

(b)