ISRO | ISRO CS 2018 | Question 53
Consider the following code segment:
int f (int x)
{
if (x < 1) return 1;
else return (f(x-1) + g(x))
}
int g (int x)
{
if (x < 2) return 2;
else return (f(x-1) + g(x/2));
}
Of the following, which best describes the growth of f(x) as a function of x?
(A)
Cubic
(B)
Quadratic
(C)
Exponential
(D)
Linear
Answer: (C)
Explanation:
f(n) = f(n-1) + g(n) ----> 1
g(n) = f(n-1) + g(n/2) ----> 2
Putting the value of g(n) in equation 1,
f(n) = 2*f(n-1) + g(n/2)
So, we can derive the below equation,
f(n) > 2f(n-1)
f(n) > 2*2*f(n-2), because f(n) > 2*f(n-1), so, f(n-1) > 2*f(n-2)
So we can write f(n) > 2*2*f(n-2)
so on....
=> f(n) > (2^n)f(1)
So, f(n) > Theta(2^n)
So option C is correct.
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Last Updated :
08 Jun, 2019
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