is-subsequence.rb

# @param {String} s
# @param {String} t
# @return {Boolean}
# def is_subsequence(s, t)
#   i = 0
#   t.each_char do |c|
#       i += 1 if c == s[i]
#   end
#   i == s.length
# end

def is_subsequence(s, t)
    return s == t if s.length == t.length
    
    j = 0
    last_found_index = 0
    found = 0
    loop do
        for x in last_found_index..((t.length-last_found_index)/2+last_found_index) do
            if s[j] == t[x]
                found = 1
                j+=1
                last_found_index = x+1
                break
            elsif last_found_index == (t.length-1)
                last_found_index = x+1
                found = 0
            else
                found = 0
            end
        end
        
        if found == 0 
            last_found_index = (t.length-last_found_index)/2+last_found_index
        end
        break if j == s.length
        break if last_found_index >= t.length
    end
    j == s.length
end