Arrays

Question

What does the following mean:
a. int arr[] = new int[3] (Setting the elements in the array to 3??)
b. arr[i] = i;

QUIZ QUESTION I'M STUCK ON
What is the output of this code?
int arr[ ] = new int[3];
for (int i = 0; i < 3; i++) {
arr[i] = i;
}
int res = arr[0] + arr[2];
System.out.println(res);

Answer 1

I'll try to explain it res = 0 + 2 => 2 ( because arr[0] = 0 and arr[2] = 2). In a. there's an array initialization with length 3. In b. it's setting the values of the elements in the array. You didn't mention the initial value of the variable res ( I suppose it's 0, if it is other you just need to add it to 2).

Answer 2

int arr[] = new int[3]
- create a new array which can contain 3 integers
arr[i] = i
- all arrays start at the 0 index
- the loop basically populates the values of the array with the value of i

This is what happens with the loop:
1st iteration - i = 0 therefore arr[0]=0 Increment i -> i = 1
2nd iteration - i = 1 therefore arr[1]=1
Increment i -> i = 2
3rd iteration - i = 2 therefore arr[2]=2
Increment i -> i = 3
4th iteration - i = 3 -> loop stops because of condition i < 3 which is now false

arr[0]=0
arr[2]=2
*value of res was not initialized, maybe equal to 0?
int res = arr[0] + arr[1];
res = 2