[leetcode] 387. First Unique Character in a String
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Question:
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.
Solution:
扫描一遍记录每个字母个数,扫描第二遍发现个数为1的就返回。不知道还有没有更简单的方法,这个方法没什么技术含量。
时间复杂度: O(n)
空间复杂度: O(n)
class Solution {public: int firstUniqChar(string s) { if (s.size() == 0) { return -1; } map<char, int> m; for (int i = 0; i < s.size(); i++) { if (m.find(s[i]) == m.end()) { m[s[i]] = 1; } else { m[s[i]]++; } } for (int i = 0; i < s.size(); i++) { if (m[s[i]] == 1) { return i; } } return -1; }};
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