387 First Unique Character in a String

Original Description: Given a string, find the first non-repeating character in it and return it’s index. If it doesn’t exist, return -1.

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• 要求： 给一个string, 找出其中第一个没有重复出现的字母

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• 返回： 该字母的index

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• 例子：
  • input: “leetcode”
  • output: 0

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Solution

• 遍历string中的字母， 使用dict存储字母的index和出现次数。
• 以index为key排序，如果出现次数==1,则输出该字母。

class Solution(object):
    def firstUniqChar(self, s):
        """
        :type s: str
        :rtype: int
        """
        if s == "":
            return -1
        elif len(s) == 1:
            return 0
        else:
            d = {}
            for i in range(len(s)):
                if s[i] not in d:
                    d[s[i]] = [1, i]
                else:
                    d[s[i]][0]+=1
            vlist = list(d.values())
            sorted_list = sorted(vlist, key=lambda x:x[1])
            count = 0
            for x in sorted_list:
                if x[0] ==1:
                    return x[1]
                else:
                    count +=1
                    if count == len(set(s)):
                        return -1