LeetCode First Unique Character in a String 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.

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本题要求找出字符串中第一个没有重复出现的字符。简单题，先对所有字符hash，找出字符和频率的对应关系，然后遍历字符串，返回第一个频率为1的字符。完整代码如下： [cpp] class Solution { public: int firstUniqChar(string s) { unordered_map<char, int> hash; for (int i = 0; i < s.size(); ++i) { ++hash[s[i]]; } for (int i = 0; i < s.size(); ++i) { if (hash[s[i]] == 1)return i; } return -1; } }; [/cpp] 本代码提交AC，用时92MS。]]>