題目

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.

難度

Easy

方法

先用一個(gè)dict統(tǒng)計(jì)每個(gè)單詞出現(xiàn)的次數(shù)，然后從頭開始檢查s的字符，如果字符出現(xiàn)次數(shù)為1，則返回該字符的位置; 如果所有字符出現(xiàn)字?jǐn)?shù)都不為1，則返回-1

python代碼

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