387. First Unique Character in a String

Easy

Given a string s, find the first non-repeating character in it and return its index. If it does not exist, return -1.

Example 1:

Input: s = "leetcode"
Output:
 0

Example 2:

Input: s = "loveleetcode"
Output:
 2

Example 3:

Input: s = "aabb"
Output:
 -1

Constraints:

• 1 <= s.length <= 105

• s consists of only lowercase English letters.

解題

Runtime: 9 ms, faster than 93.92%

Memory Usage: 5.4 MB, less than 78.65%

func firstUniqChar(s string) int {
    arr := make([]int, 26)
    
    for i := 0; i < len(s); i++ {
        arr[s[i] - 'a']++
    }
    
    for i := 0; i < len(s); i++ {
        if arr[s[i] - 'a'] == 1 {
            return i
        }
    }
    
    return -1
}