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- #!/usr/bin/ruby
- # A perfect square N has a splitting representation (S) if it's possible to segment
- # the decimal representation of N into a list of integers L, such that sum(L) = sqrt(n).
- # See also:
- # https://oeis.org/A104113
- # https://projecteuler.net/problem=719
- func S_representation(n) {
- var v = n.isqrt
- var D = n.digits
- for k in (1 .. D.len>>1) {
- combinations(D.len, k, {|*indices|
- var t = D.segment(indices...)
- if (t.sum{.digits2num} == v) {
- return t
- }
- })
- }
- return []
- }
- File(ARGV[0] \\ "data.txt").open_r.each{|line|
- var n = line.nums.tail
- n > 1 || next
- var arr = S_representation(n)
- assert(arr.len > 0)
- say ("sqrt(#{n}) = ", arr.flip.map{.digits2num}.grep.join(' + '))
- }
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