Leetcode 387 problem.

A function to find the first non-repeating character in it and return its index. If it does not exist, it returns -1.

Go

• Time complexity: $O(n^{2})$ - n is a length of a string
• Auxiliary space: $O(1)$ - constant amount of space

func firstUniqChar(s string) int {
    for index, rune := range s {
        frequency := strings.Count(s, string(rune))

        if (frequency == 1) {
            return index
        }
    }

    return -1
}