Hi I have a homework question that needs some clarifications,
1.
public int f (int n) {
if (n < 0)
return 2;
else
return f (n - 1) + f (n - 3);
}
what is the value when the recall is f(3) I know that this loops so
f(3) = f(2)+2
= f(1)+2+2
= f(0)+2+2+2
= 8
but I'm not sure if Java considers 0 less than 0.
Java does not consider 0 less than 0.
Arrays use a zero-based numbering system, so the last index is going to be the length of the array (the initialized size, 10 in this case) minus one. This is essentially a left-shift from
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
to
0, 1, 2, 3, 4, 5, 6, 7, 8, 9
So
names[names.length] = "Hello";
will throw an exception, as names.length will get the number of elements in the array, but will not get the last index in the array.
0 is not less than 0. It is equal to 0. Use <= for "less than or equal to".
f(3) = f(3-1) + f(3-3)
f(3) = f(2) + f(0)
f(2) = f(2-1) + f(2-3)
f(2) = f(1) + f(-1)
f(1) = f(1-1) + f(1-3)
f(1) = f(0) + f(-2)
f(0) = f(-1) + f(-2)
f(N<0) = 2
Work your way back up.
f(0) = 2+2
f(1) = 2+2 +2
f(2) = 2+2+2 +2
f(3) = 2+2+2+2 +2+2
