GATE | GATE-CS-2015 (Set 3) | Question 49

Consider the following recursive JAVA function. If get(6) function is being called in main() then how many times will the get() function be invoked before returning to the main()? 

Java

static void get (int n){
  if (n < 1)
    return;
  get(n - 1);
  get(n - 3);
  System.out.print(n);
}

(A)

15

(B)

25

(C)

35

(D)

45

Answer: (B)

Explanation:

                              get(6) [25 Calls]
                              /      \\
               [17 Calls] get(5)       get(3) [7 Calls]
                        /     \\
                    get(4)    get(2)[5 Calls]
                   /    \\ 
     [7 Calls] get(3)  get(1)[3 Calls]
                /     \\
             get(2)   get(0)
            /    \\
[3 Calls]get(1)  get(-1) 
   /  \\
get(0) get(-2)

We can verify the same by running below program. 

CPP

# include <stdio.h>
int count = 0;

void get (int n)
{
    count++;
    if (n < 1) return;
    get(n-1);
    get(n-3);
}
int main()
{
    get(6);
    printf(\"%d \", count);
}

Output: 25

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