Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.
Examples:
s = "leetcode"
return 0.
s = "loveleetcode",
return 2.
class Solution {
public:
int firstUniqChar(string s) {
int arr['z'+1] = {0};
for(int i=0;i<s.size();i++) arr[s[i]] += 1;
for(int i=0;i<s.size();i++){
if(arr[s[i]] == 1) return i;
}
return -1;
}
};
