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.
这道题确实没有什么难度，我们只要用哈希表建立每个字符和其出现次数的映射，然后按顺序遍历字符串，找到第一个出现次数为1的字符，返回其位置即可，参见代码如下：
class Solution { public: int firstUniqChar(string s) { unordered_map<char, int> m; for (char c : s) ++m[c]; for (int i = 0; i < s.size(); ++i) { if (m[s[i]] == 1) return i; } return -1; } };
本文转自博客园Grandyang的博客，原文链接：字符串第一个不同字符[LeetCode] First Unique Character in a String ，如需转载请自行联系原博主。
