GATE | GATE CS 2011 | Question 49

Consider the same recursive C++ function that takes two arguments 

C++

unsigned int foo(unsigned int n, unsigned int r) {
  if (n  > 0) return (n%r +  foo (n/r, r ));
  else return 0;
}

What is the return value of the function foo when it is called as foo(513, 2)?

(A)

9

(B)

8

(C)

5

(D)

2

Answer: (D)

Explanation:

foo(513, 2) will return 1 + foo(256, 2). All subsequent recursive calls (including foo(256, 2)) will return 0 + foo(n/2, 2) except the last call foo(1, 2) . The last call foo(1, 2) returns 1. So, the value returned by foo(513, 2) is 1 + 0 + 0…. + 0 + 1. The function foo(n, 2) basically returns sum of bits (or count of set bits) in the number n.

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