What is the return value of f(p,p), if the value of p is initialized to 5 before the call? Note that the first parameter is passed by reference, whereas the second parameter is passed by value.

int f (int &x, int c) {
c = c - 1;
if (c == 0) return 1;
x = x + 1;
return f(x, c) * x;
}

Question

What is the return value of f(p,p), if the value of p is initialized to 5 before the call? Note that the first parameter is passed by reference, whereas the second parameter is passed by value.

int f (int &x, int c) {
 c = c - 1;
 if (c == 0) return 1;
 x = x + 1;
 return f(x, c) * x;
}

Accepted Answer

6561. Because x is passed by reference, all recursive frames share it. The recursion increments x to 6,7,8,9 until c reaches 0, so at unwind x=9 everywhere; the product is 1 * 9 * 9 * 9 * 9 = 9^4 = 6561, not 161051.

What is the return value of f(p,p), if the value of p is initialized to 5 before the call? Note that the first parameter is passed by reference, whereas the second parameter is passed by value. int f (int &x, int c) { c = c - 1; if (c == 0) return 1; x = x + 1; return f(x, c) * x; }

Solution

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