[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:

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

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