Cracking the Coding Interview, Fourth Edition

150 Days of Programming Problems

#!/usr/bin/ruby

def allUnique(s)
    seen = Hash.new()
    s.each_char do |c|
        if seen[c] then
            return false
        else
            seen[c] = true
        end
    end
    return true
end

def allUniqueBit(s)
    seen = 2**129
    s.each_byte do |b|
        if 2**b | seen == seen
            return false
        else
            seen = seen | 2**b
        end
    end
    return true
end