> For the complete documentation index, see [llms.txt](https://lex47.gitbook.io/leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://lex47.gitbook.io/leetcode/leet-solution-ruby/387.md).

# 387. First Unique Character in a String

Given a string, find the first non-repeating character in it and return its index. If it doesn't exist, return -1.

**Examples:**

```
s = "leetcode"
return 0.

s = "loveleetcode"
return 2.
```

```
# @param {String} s
# @return {Integer}
def first_uniq_char(s)
  return -1 if s.chars.empty?
  hash = Hash[s.chars.group_by{|x| x}.map{|k,v|[k,v.size]}]
  arr = hash.select{|k,v| v == 1}
  if arr.empty?
    -1
  else
    s.index(arr.first[0])
  end
end
```