Question

For each call to the following method, indicate what console output is produced:

public void mystery2(int n) {
    if (n <= 1) {
        System.out.print(n);
    } else {
        mystery2(n / 2);
        System.out.print(", " + n);
    }
}

mystery2(1);
mystery2(4);
mystery2(16);
mystery2(30);
mystery2(100);

Answer 1

Solution:

Here in the given mystery2() function it is checking whether the n value is less than or equals to 1 if yes print(n) value otherwise call mystery2() by dividing n with 2 . Here after the function call the print statement will execute.

when we call mystery2(1) it will print the value 1 because n<=1 is becomes true so it will print 1.

when we call mystery2(4) it will print 1,2,4

because here n=4 so n<=1 becomes false so it will call mystery2(n/2) = mystery2(2) after execution of mystery2(1) it will print value 4

so in next step n=2 so n<=1 becomes false so it will call mystery2(2/2)= mystery2(1) after execution of mystery2(1) it will print value 2

Here n=1 so n<=1 becomes true so it will print value 1 and executes the print statements after the previous recursive calls.

n	Condition	func call	remaining statements need to execute
		mystery2(4)
4	4<=1 false	mystery2(4/2)	print(n) =4
2	2<=1 false	mystery2(2/2)	print(n)=2
1	1<=1 true		print(n)=1

i.e 1,2,4

when we call mystery2(16) output is 1,2,4,8,16

so

n	Condition	func call	remaining statements need to execute
		mystery2(16)
16	16<=1 = false	mystery2(16/2)	print(n) = 16
8	8<=1 false	mystery2(8/2)	print(n) =8
4	4<=1 false	mystery2(4/2)	print(n) =4
2	2<=1 false	mystery2(2/2)	print(n)=2
1	1<=1 true		print(n)=1

when we call mystery2(30) output is 1,3,7,15,30

n	Condition	func call	remaining statements need to execute
		mystery2(30)
30	30<=1 = false	mystery2(30/2)	print(n) = 30
15	15<=1 false	mystery2(15/2)	print(n) =15
7	7<=1 false	mystery2(7/2)	print(n) =7
3	3<=1 false	mystery2(3/2)	print(n)=3
1	1<=1 true		print(n)=1

when we call mystery2(100) output is 1,3,6,12,25,50,100

n	Condition	func call	remaining statements need to execute
		mystery2(100)
100	100<=1 = false	mystery2(100/2)	print(n) = 100
50	50<=1 false	mystery2(50/2)	print(n) =50
25	25<=1 false	mystery2(25/2)	print(n) =25
12	12<=1 false	mystery2(12/2)	print(n)=12
6	6<=1 false	mystery2(6/2)	print(n)=6
3	3<=1 false	mystery2(3/2)	print(n)=3
1	1<=1 true		print(n)=1

Note:Here remaining statements will execute from bottom to top. Also print statement includes commas.

mystery2(1) = 1                                                                                                                             

mystery2(4) = 1, 2, 4                                                                                                                       

mystery2(16) = 1, 2, 4, 8, 16                                                                                                                

mystery2(30) =1, 3, 7, 15, 30                                                                                                               

mystery2(100) = 1, 3, 6, 12, 25, 50, 100  

Note: if you have any queries please post a comment thanks a lot.. always avaiable to help you...