Problem 42291. GJam 2015 Rd1B: Counter Culture

This Challenge is derived from GJam 2015 Rd 1B: Counter Culture. Fastest completion - 5 minutes.

Determine minimum sequence length to reach a number. Sequence starts at 1 and the next is either +1 or the number's reverse with trailing zeros removed. (eg 2300 is followed by 2301 or 32)

Input: N, a value from 1 to 1,000,000

Output: L, minimum length of sequence to reach N

Examples: Small Case 1<=N<=1000000

N=5,  L=5  [1 2 3 4 5] L=N is true thru 19
N=23, L=15 [1:12 21 22 23]

Theory: The small case can be solved with brute force or semi-brute force using storage of past calculations. All values are processed at each depth level. Duplicates from [N+1 and flip] are purged. A fast reversal function is essential. Direct summation works well. The large case N limit is 1E14 making even semi-brute force with storage unlikely.

Additional GJam solutions can be found at Example GJam Matlab solutions. Select Find Solutions, change Language to Matlab. The Test Suite, at the bottom, contains a full GJam Matlab solution.

Solution Stats

72.41% Correct | 27.59% Incorrect
Last Solution submitted on Jun 12, 2020

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