[LeetCode]387. First Unique Character in a String

题目

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

Examples:

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s = "leetcode"
return 0.

s = "loveleetcode",
return 2.

Note: You may assume the string contain only lowercase letters.

难度

Easy

方法

先用一个dict统计每个单词出现的次数,然后从头开始检查s的字符,如果字符出现次数为1,则返回该字符的位置; 如果所有字符出现字数都不为1,则返回-1

python代码

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class Solution(object):
def firstUniqChar(self, s):
"""
:type s: str
:rtype: int
"""
counter = {}
for c in s:
if counter.has_key(c):
counter[c] += 1
else:
counter[c] = 1

for i in range(len(s)):
if counter[s[i]] == 1:
return i
return -1

assert Solution().firstUniqChar("leetcode") == 0
assert Solution().firstUniqChar("leveleetcode") == 2