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Challenges

Comments on Length of a Sumac Sequence

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Length of a Sumac Sequence

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Heavily based on this closed challenge from SE.

Description

A Sumac sequence starts with two non-zero integers $t_1$ and $t_2.$

The next term, $t_3 = t_1 - t_2$

More generally, $t_n = t_{n-2} - t_{n-1}$

The sequence ends when $t_n ≤ 0$. All values in the sequence must be positive.

Challenge

Given two integers $t_1$ and $t_2$, compute the Sumac sequence, and output it's length.

If there is a negative number in the input, remove everything after it, and compute the length.

You may take the input in any way (Array, two numbers, etc.)

Test Cases

(Sequence is included for clarification)

[t1,t2]   Sequence          n
------------------------------
[120,71]  [120,71,49,22,27] 5
[101,42]  [101,42,59]       3
[500,499] [500,499,1,498]   4
[387,1]   [387,1,386]       3
[3,-128]  [3]               1
[-2,3]    []                0
[3,2]     [3,2,1,1]         4

Scoring

This is code-golf. Shortest answer in each language wins.

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1 comment thread

General comments (4 comments)
General comments
celtschk‭ wrote over 3 years ago

What should be the result for t1=t2=0?

Razetime‭ wrote over 3 years ago

@celtschk sequence ends when tn is ≤ 0, so it should be 0.

celtschk‭ wrote over 3 years ago

@Razetime: You should probably add that as a test case, as several currently posted solutions fail in this case.

Razetime‭ wrote over 3 years ago

ok, added it in.