June 2018 Update

Task/Non-continuous-subsequences/Julia/non-continuous-subsequences.julia

@@ -0,0 +1,56 @@
+iscontseq(n::Integer) = count_zeros(n) == leading_zeros(n) + trailing_zeros(n)
+iscontseq(n::BigInt)  = !ismatch(r"0", rstrip(bin(n), '0'))
+
+function makeint2seq(n::Integer)
+    const idex = collect(1:n)
+    function int2seq(m::Integer)
+        d = digits(m, 2, n)
+        idex[d .== 1]
+    end
+    return int2seq
+end
+
+struct NCSubSeq{T<:Integer}
+    n::T
+end
+
+mutable struct NCSubState{T<:Integer}
+    m::T
+    m2s::Function
+end
+
+Base.iteratorsize(::NCSubSeq) = Base.HasLength()
+Base.length(a::NCSubSeq) = 2 ^ a.n - a.n * (a.n + 1) ÷ 2 - 1
+
+Base.start(a::NCSubSeq) = NCSubState(5, makeint2seq(a.n))
+Base.done(a::NCSubSeq, as::NCSubState) = 2 ^ a.n - 3 < as.m
+function Base.next(a::NCSubSeq, as::NCSubState)
+    s = as.m2s(as.m)
+    as.m += 1
+    while iscontseq(as.m)
+        as.m += 1
+    end
+    return (s, as)
+end
+
+n = 4
+println("Testing NCSubSeq for ", n, " items:\n ", join(NCSubSeq(n), " "))
+
+s = "Rosetta"
+cs = split(s, "")
+m = 10
+n = length(NCSubSeq(length(s))) - m
+println("\nThe first and last ", m, " NC sub-sequences of \"", s, "\":")
+for (i, a) in enumerate(NCSubSeq(length(cs)))
+    i <= m || n < i || continue
+    println(@sprintf "%6d %s" i join(cs[a], ""))
+    i == m || continue
+    println("    .. ......")
+end
+
+using IterTools.chain
+
+println("\nThe first and last ", m, " NC sub-sequences of \"", s, "\"")
+for x in IterTools.chain(1:10, 20:10:40, big.(50:50:200))
+    @printf "%7d → %d\n" x length(NCSubSeq(x))
+end