LeetCode First Unique Character in a String

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.


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:

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;
	}
};

本代码提交AC,用时92MS。

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