Created
August 5, 2012 18:37
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MAXSIZE = 1000000 | |
MEMO = Array.new(MAXSIZE) | |
def collatz_size(i) | |
size = 0 | |
n = i | |
while n != 1 do | |
if n <= MAXSIZE && MEMO[n] | |
size += MEMO[n] | |
break | |
else | |
n = n.even? ? n/2 : 3*n + 1 | |
size += 1 | |
end | |
end | |
MEMO[i] = size #メモ化 | |
end | |
max = (1...MAXSIZE).each.map do |i| | |
{ input: i, count: collatz_size(i) } | |
end.max {|i, j| i[:count] <=> j[:count] } | |
puts max[:input] | |
# 837799 | |
# 3.2s CPU: Core i5 1.6GHz, MEM: 4G |
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