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.

 

Note: You may assume the string contain only lowercase letters.

1 class Solution { 2 public: 3     int firstUniqChar(string s) { 4         int table[26] = {
   0}; 5         for (char ch : s) 6             table[ch - 'a']++; 7          8         for (int i = 0; i < s.size(); i++) 9             if (table[s[i] - 'a'] == 1) return i;10             11         return -1;12     }13 };

 

1 class Solution { 2 public: 3     int firstUniqChar(string s) { 4         unordered_map
     
       um; 5         for (int i = 0; i < s.size(); i++) { 6             if (!um[s[i]] && s.find(s[i], i + 1) == s.npos) return i; 7             um[s[i]] = true; 8         } 9         return -1;10     }11 };
     

 

1 class Solution { 2 public: 3     int firstUniqChar(string s) { 4         unordered_map
     

> um; 5 for (int i = 0; i < s.size(); i++) 6 um[s[i]].push_back(i); 7 8 int result = INT_MAX; 9 for (auto item : um) {10 if (item.second.size() == 1) result = min(result, item.second[0]);11 }12 return result == INT_MAX ? -1 : result;13 }14 };