[leetcoe] 387. First Unique Character in a String @ python

最新推荐文章于 2023-12-22 02:10:49 发布

原创最新推荐文章于 2023-12-22 02:10:49 发布 · 161 阅读

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本文深入探讨了一种高效算法，用于在字符串中查找第一个不重复的字符，并详细解释了其实现过程。通过使用字典记录字符出现频率，再遍历字符串定位目标字符，此方法在时间和空间复杂度上表现优异。

原题

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.

解法

先用字典存储每个字符出现的次数, 然后遍历字符串, 当出现字母次数为1时, 返回当前index.
Time: 2*O(n)
Space: O(1)

代码

class Solution(object):
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        count = collections.Counter(s)
        for i, char in enumerate(s):
            if count[char] == 1:
                return i
        return -1