What is the value of result after the code executes:
int[] a = new int[] {1, 1, 2, 3, 5};
int[] b = new int[] {a.length, a[0]+a[1], a[1]+a[2], 10};
int[] c = a;
int[] d = b;
c[0] = d[2];
a[1] = b[3];
a = b;
d = c;
b = d;
b[3] = a[b[0]];
int result = a[0] + b[1] + c[2] + d[3];
To start this problem lets first write out the arrays and the values they contain.
a is easy because the values are declared for us.
a [1, 1, 2, 3, 5]
b has the following values
[length of a = 5, 1 + 1, 1 + 2, 10]
b [5, 2, 3, 10]
c is just a variable that is pointing to the same thing as a.
d is just a variable pointing to b
So in the end we have this
a, c [1, 1, 2, 3, 5]
b, d [5, 2, 3, 10]
Now if we use a reference to c at this point, we are just going to rewrite it as a, and d will be re-written as b.
c[0] = d[2]; will be the same as a[0] = b[2];
so now index 0 will be the value of b at index 2.
a [3, 1, 2, 3, 5]
a[1] = b[3]; will just swap the value of a at 1 for the value of b at 3.
a [3, 10, 2, 3, 5]
Now we have to deal with the swapping.
a = b;
d = c;
b = d;
a = b means that a will now point to the same thing as b. At this point,
everything but c is pointing to the array that was b.
This is the result:
b, c, d [5, 2, 3, 10]
d = c points the d array back to the array that was originally a.
b, a [5, 2, 3, 10]
d, c [3, 10, 2, 3, 5]
finally b = d assigns b back to the other array.
a [5, 2, 3, 10]
b, d, c [3, 10, 2, 3, 5]
b[3] = a[b[0]];
b[0] is 3
a[3] is 10
so we switch b[3] to 10 which leaves us with.
a [5, 2, 3, 10]
b, d, c [3, 10, 2, 10, 5]
finally
int result = a[0] + b[1] + c[2] + d[3];
result = 5 + 10 + 2 + 10 = 27