返回ruby中字符串中所有字符出现的索引

str = "hello world"
indexes = {}

str.chars.each_with_index do |char, index|
  if indexes[char]
    indexes[char]<< index
  else
    indexes[char] = [index]
  end
end

indexes.each do |char, indices|
  puts "#{char}: #{indices.join(', ')}"
end

h: 0
e: 1
l: 2, 3
o: 4, 7
 : 5
w: 6
r: 8
d: 9