public class Solution {
    public int FirstNotRepeatingChar(String str) {
        int[] vis = new int[252];
        for(int i = 0; i < str.length(); i++){
            vis[str.charAt(i)-'A']++;
        }
        for(int i = 0; i < str.length(); i++){
            if(vis[str.charAt(i)-'A'] == 1){
                return i;
            }
        }
        return -1;
    }
}