Consider the following definition of the recursive function mystery. What is the output of the following statement?
Cout

Question

Consider the following definition of the recursive function mystery. What is the output of the following statement?
Cout << mystery(6, 10) << endl;

A) 13 
B) 21 
C) 40 
D) 42

Quizplus · Accepted Answer

The function mystery takes two integer parameters: x and y. If x is equal to 0, the function returns y. If x is greater than 0, the function recursively calls itself with updated parameters (x-1, y+x).

In this case, the initial call is mystery(6, 10). The function will make the following calls:
mystery(6, 10) -> mystery(5, 16) -> mystery(4, 21) -> mystery(3, 25) -> mystery(2, 28) -> mystery(1, 30) -> mystery(0, 31)
When x equals 0, the function returns the second parameter y which is 31. Therefore, the output of the statement is 31+1+2+3+4 = 21.

Consider the Following Definition of the Recursive Function Mystery