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Question 1:
Solution to Question 1:
Let's analyze the
mystery method step by step for the input 1234.Method Breakdown:
Execution Steps for
mystery(1234):- First Call:
mystery(1234) - Print:
1234 % 10→4 - Check:
1234 / 10→123(not zero) - Recursive Call:
mystery(123)
- Second Call:
mystery(123) - Print:
123 % 10→3 - Check:
123 / 10→12(not zero) - Recursive Call:
mystery(12)
- Third Call:
mystery(12) - Print:
12 % 10→2 - Check:
12 / 10→1(not zero) - Recursive Call:
mystery(1)
- Fourth Call:
mystery(1) - Print:
1 % 10→1 - Check:
1 / 10→0(termination condition) - Print Again:
1 % 10→1 - Return to Third Call
- Returning to Third Call:
mystery(12) - Print Again:
12 % 10→2 - Return to Second Call
- Returning to Second Call:
mystery(123) - Print Again:
123 % 10→3 - Return to First Call
- Returning to First Call:
mystery(1234) - Print Again:
1234 % 10→4
Sequence of Prints:
- From First Call:
4
- From Second Call:
3
- From Third Call:
2
- From Fourth Call:
1and1
- Returning to Third Call:
2
- Returning to Second Call:
3
- Returning to First Call:
4
Final Output:
43211234Answer:
(D) 43211234
Question 1:
Solutions to Question 2:
First, let's trace the execution step-by-step. The given method is:
We are interested in
recur(27).- Call
recur(27): - Since 27 > 10, it doesn't return immediately. Instead, it will return
recur(recur(27 / 3)). - Compute 27/3 = 9, so this becomes
recur(recur(9)).
- Call
recur(9): - Since 9 ≤ 10, it returns 9 * 2 = 18.
- So
recur(9) = 18. recur(27) = recur(18).
Substituting back into the original call:
- Call
recur(18): - 18 > 10, so it returns
recur(recur(18 / 3)). - Compute 18/3 = 6, so this becomes
recur(recur(6)).
- Call
recur(6): - 6 ≤ 10, so return 6 * 2 = 12.
- Thus
recur(6) = 12. recur(18) = recur(12).
Substitute this back:
- Call
recur(12): - 12 > 10, so it returns
recur(recur(12 / 3)). - Compute 12/3 = 4, so this becomes
recur(recur(4)).
- Call
recur(4): - 4 ≤ 10, so return 4 * 2 = 8.
- Thus
recur(4) = 8. recur(12) = recur(8).
Substitute this back:
- Call
recur(8): - 8 ≤ 10, so return 8 * 2 = 16.
- Thus
recur(8) = 16.
Substituting all the way back up:
recur(12) = 16
recur(18) = recur(12) = 16
recur(27) = recur(18) = 16
Final Answer: 16
This corresponds to choice (D).
- 作者:现代数学启蒙
- 链接:https://www.math1234567.com/csa001questions
- 声明:本文采用 CC BY-NC-SA 4.0 许可协议，转载请注明出处。
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