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 <= 105s consists of only lowercase English letters.class Solution {
public:
int firstUniqChar(string s) {
map <char, int> m;
for (int i=0; i<s.length(); i++){
m[s[i]]++;
}
for (int i=0; i<s.length(); i++){
if (m[s[i]]==1)
return i;
}
return -1;
}
};