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

版权声明：版权归个人所有，未经博主允许，禁止转载 https://blog.csdn.net/danspace1/article/details/86556521

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