> For the complete documentation index, see [llms.txt](https://timmybeeflin.gitbook.io/cracking-leetcode/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://timmybeeflin.gitbook.io/cracking-leetcode/hashtable/387.-first-unique-character-in-a-string.md).

# 387. First Unique Character in a String

T: O(n)

S: O(1)

```java
class Solution {
    public int firstUniqChar(String s) {
        char[] map = new char[26];
        for (char c : s.toCharArray()) {
            map[c - 'a']++;
        }
        for (int i = 0; i < s.length(); i++) {
            if (map[s.charAt(i) - 'a'] == 1) {
                return i;
            }
        }
        return -1;
    }
}
```