72 lines
2.2 KiB
Julia
Executable File
72 lines
2.2 KiB
Julia
Executable File
# String with Length
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# This allows to compute length once and only once
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struct StringWithLength{T<:AbstractString} <: AbstractString
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s::T
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l::Int
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end
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string_with_length(s::AbstractString) = StringWithLength(s, length(s))
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Base.length(s::StringWithLength) = s.l
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Base.iterate(s::StringWithLength, i::Integer = firstindex(s.s)) = iterate(s.s, i)
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Base.nextind(s::StringWithLength, i::Int, n::Int = 1) = nextind(s.s, i, n)
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Base.ncodeunits(s::StringWithLength) = ncodeunits(s.s)
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Base.isvalid(s::StringWithLength, i::Int) = isvalid(s.s, i)
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function reorder(s1::AbstractString, s2::AbstractString)
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s1 = string_with_length(s1)
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s2 = string_with_length(s2)
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if length(s1) <= length(s2)
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return s1, s2
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else
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return s2, s1
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end
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end
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## Find common prefixes (up to lim. -1 means Inf)
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function remove_prefix(s1::AbstractString, s2::AbstractString, lim::Integer = -1)
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l = 0
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x1 = iterate(s1)
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x2 = iterate(s2)
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while (x1 !== nothing) & (x2 !== nothing) & (l < lim || lim < 0)
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ch1, state1 = x1
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ch2, state2 = x2
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ch1 != ch2 && break
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x1 = iterate(s1, state1)
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x2 = iterate(s2, state2)
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l += 1
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end
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return l, x1, x2
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end
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# Return start of commn substring in s1, start of common substring in s2, and length of substring
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# Indexes refer to character number, not index
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function longest_common_substring(s1::AbstractString, s2::AbstractString, len1::Integer, len2::Integer)
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if len1 > len2
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start2, start1, len = longest_common_substring(s2, s1, len2, len1)
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else
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start1, start2, len = 0, 0, 0
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p = zeros(Int, len2)
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i1 = 0
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for ch1 in s1
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i1 += 1
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i2 = 0
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oldp = 0
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for ch2 in s2
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i2 += 1
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newp = 0
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if ch1 == ch2
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newp = oldp > 0 ? oldp : i2
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currentlength = (i2 - newp + 1)
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if currentlength > len
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start1, start2, len = i1 - currentlength + 1, newp, currentlength
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end
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end
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p[i2], oldp = newp, p[i2]
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end
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end
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end
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return start1, start2, len
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end
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