CODEWITHSUNDEEP
javarecursion
Rae
Rae

Reputation: 83

How is the result produce in a recursion?

First Code: a = 5

    if (a==0)
        return 1;

    return a * xample(a-1);

My tracing:

5==0 FALSE skip return 1 return 5 * xample(5-1) so, a = 4

go back inside the method 4==0 FALSE skip return 1 return 5 * xample(4-1) so, a = 3

go back inside the method 3==0 FALSE skip return 1 return 5 * xample(3-1) so, a = 2

go back inside the method 2==0 FALSE skip return 1 return 5 * xample(2-1) so, a = 1

go back inside the method 1==0 FALSE skip return 1 return 5 * xample(1-1) so, a = 0

go back inside the method 0==0 TRUE return 1

so last value is 1, how come the real last value is 120?

Second Code: a = 5

    if (a<1)
        return 1;
    else
        return a + xample(a/5);

how come the answer is 7?

Third Code: a = 5

    a--;
    if (a>0)
    {
        xample(a);
    }
    return a;

How come the answer is 4???

Upvotes: 0

Views: 66

Answers (1)

Eran
Eran

Reputation: 393821

In the following code :

if (a==0)
    return 1;

return a * xample(a-1);

If a is 5 :

return 5 * xample (5 - 1) = 
       5 * 4 * xample (4 - 1) =
       5 * 4 * 3 * xample (3 - 1) =
       5 * 4 * 3 * 2 * xample (2 - 1) =
       5 * 4 * 3 * 2 * 1 * xample (1 - 1) =
       5 * 4 * 3 * 2 * 1 * 1 = 120

Upvotes: 3

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