Leetcode学习（38）—— 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.

class Solution(object):
def firstUniqChar(self, s):
dic = {}
index_list = []
for i in s:
if i not in dic.keys():
dic[i] = 1
else:
dic[i] += 1
if 1 not in dic.values():
return -1
for key, value in dic.items():
if value == 1:
index_list.append(list(s).index(key))
return min(index_list)

import string
class Solution(object):
def firstUniqChar(self, s):
return min([s.find(c) for c in string.ascii_lowercase if s.count(c) == 1] or [-1])

策略：遍历 26 个小写字母（降低算法的时间复杂度），当在 s 中 c 的是数量为 1 的时候，在 s 中找到 c 的位置。

当 s 中不存在 数量为1 的字母时，第一个 list 为 空

In [31]: min([] or [-1])
Out[31]: -1