Python解法：哈希

class Solution:
    def FirstNotRepeatingChar(self, s):
        # write code here
        l=[0]*256
        for i in s:#记录每个字符出现的次数
            l[ord(i)]+=1
        for j,v in enumerate(s):#再按照s的顺序去查看l中次数为1的字符
            if l[ord(v)]==1:
                return j
        return -1

另外也可以借助计数字典实现，代码如下：

from collections import Counter
class Solution:
    def FirstNotRepeatingChar(self, s):
        # write code here
        dict=Counter(s)
        for j,v in enumerate(s):
            if dict[v]==1:
                return j
        return -1