Zabe - 1 year ago 73
C++ Question

# How do I write a loop function as a recursive function?

Well, I've been trying to rework this many times. Though, at one point I thought the longestSequence function would help, since it displays the longest hailstone sequence. Though, I can't seem to figure out how to find, or store the value it used to find that.If someone could explain how, I would appreciate it.

``````int longestSequence(int n)
{
int u = n;

if(u == 1)
{
return 1;
}
else
{
return max(hailstoneLength(u), longestSequence(u-1));
}
}
``````

The part I'm having trouble with is my longest start sequence:

``````int hailLongestSeq(int n)
{
int k;
int longest = 0;
for(int j = 1; j <= n; j++)
{
if(hailstoneLength(j) > longest)
{
longest = hailstoneLength(j);
k = j;
}
}
return k;
}
``````

I'm not sure how to make this into a recursion, I noticed for some recursions I saw people using for loops still, but I was sure we weren't supposed to use loops.
It may be a dumb question, but is there a formula to translating for loops to recursions, if anyone knows one?

The expected out put is like this:

The longest hailstone sequence starting with a number up to 10 has length 20.
The longest hailstone sequence starting with a number up to 10 begins with 9.

as 9's sequence has a length of 20 numbers, and is the longest from 1 to 10.

Yes every for loop can be translated to recursive call, obviously like this:

``````for (i=0; i<N; i++) {
body;
}
``````

translate it to:

``````func(int i) {
if (i<N) { body; func(i+1) }
else return;
}

func(0);
``````

This can be easily extended to any for loop computation (add parameters if needed, return value, etc).

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