Problem 44448. Project Euler: Problem 14 Longest Collatz sequence
This problem is a hard version of "Problem 42673. Longest Collatz Sequence", because of time limits. https://ww2.mathworks.cn/matlabcentral/cody/problems/42673-longest-collatz-sequence
The following iterative sequence is defined for the set of positive integers:
n → n/2 (n is even) n → 3n + 1 (n is odd)
Using the rule above and starting with 13, we generate the following sequence:
13 → 40 → 20 → 10 → 5 → 16 → 8 → 4 → 2 → 1 It can be seen that this sequence (starting at 13 and finishing at 1) contains 10 terms. Although it has not been proved yet (Collatz Problem), it is thought that all starting numbers finish at 1.
Which starting number, no more than N, produces the longest chain, and how long? Don't cheat!
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9 Comments
Hi Athi , to get rid of this server error, please speed up your codes.
Hi goc3, now I delete the "digit test", and submit a correct solution.
Hi li haitao,
I like this problem very much. I was trying to solve it for 3 three days.
The best running time reached by my solution 1643182 is,
Test Case #9 : 1.7022 sec
Test Case #10: 17.8276 sec
Test Case #11: 15.0268 sec (Random)
Thanks for such a wonderful problem and test case.
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