387. 字符串中的第一个唯一字符

题目来源：387. 字符串中的第一个唯一字符

给定一个字符串，找到它的第一个不重复的字符，并返回它的索引。如果不存在，则返回 -1。

/**
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function(s) {
    const frequency = new Map();
    for(let c of s){
      frequency.set(c, (frequency.get(c) || 0)+1);
    }
    for (const [i, ch] of Array.from(s).entries()) {
        if (frequency.get(ch) === 1) {
            return i;
        }
    }
    return -1;
};

示例：

s = "leetcode"
返回 0

s = "loveleetcode"
返回 2

 Python3

import collections


class Solution:
    def firstUniqChar(self, s: str) -> int:
      fr = collections.Counter(s)
      for i,c in enumerate(s):
        if fr.get(c) == 1:
          return i
      return -1

      # dic = dict()
      # for c in s:
      #   dic[c] = dic.get(c, 0) + 1
      
      # index = 0
      # for [key, val] in dic.items():
      #   if val == 1:
      #     return index
      #   index += 1
      # return -1


if __name__ == '__main__':
  so = Solution()
  s = "leetcode"
  print(so.firstUniqChar(s))
  s = "loveleetcode"
  print(so.firstUniqChar(s))          

 

提示：你可以假定该字符串只包含小写字母。