てきとーに

gistfile1.rb

#!/usr/bin/ruby

def merge(ary1,ary2)
    idx1 = 0
    idx2 = 0
    result = Array.new

    while result.length < ary1.length + ary2.length
        ary1val = idx1 <= ary1.length-1 ? ary1[idx1] : -1
        ary2val = idx2 <= ary2.length-1 ? ary2[idx2] : -1

        if ary1val > ary2val
            result.push ary1val
            idx1 += 1
        else
            result.push ary2val
            idx2 += 1
        end
    end
    return result
end

def mergeSort(first, last, ary)
    if first >= last
        return
    end

    mid = ( first + last ) / 2
    mergeSort(first, mid, ary)
    mergeSort(mid+1, last, ary)

    buf1 = ary[first..mid]
    buf2 = ary[mid+1..last]

    ary[first..last] = merge(buf1,buf2)
end

N = 16
$X = Array.new(N)

for i in 0..N-1
    $X[i] = rand(N)
end


p $X

mergeSort(0, $X.length-1, $X)

p $X