387. First Unique Character in a String

Total Accepted: 41662

• Total Submissions: 91486
• Difficulty: Easy
• Contributors: Admin

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         unordered_map
        
          hash; 5         for(char c : s){ 6             hash[c]++; 7         } 8         /* 9         for(int i : hash){10             if(i == 1)11         }*///没法从hash表里判断，因为只知道value不能逆向得知hash里面的key12         //所以要从原string里找13         for(int i = 0; i < s.size(); i++){14             if(hash[s[i]] == 1){15                 return i;16             }17         }18         return -1;19     }20 };