LeetCode 389. 找不同

示例 1：

输入：s = "abcd", t = "abcde"
输出："e"
解释：'e' 是那个被添加的字母。
示例 2：

输入：s = "", t = "y"
输出："y"
示例 3：

输入：s = "a", t = "aa"
输出："a"
示例 4：

输入：s = "ae", t = "aea"
输出："a"
 ```
提示：

0 <= s.length <= 1000
t.length == s.length + 1
s 和 t 只包含小写字母

## 解题思路

def findTheDifference(self, s: str, t: str) -> str:

    from collections import Counter

    sC = dict(Counter(s)) #通过collections组件统计字符串每个字符出现的数量

    tC = dict(Counter(t))

    for key,val in tC.items():

        if (key not in sC) or (sC[key] != val):#如果不存在对应的字符就输出

            return key

    return ""

s = "abcd"

t = "abcde"

ret = Solution().findTheDifference(s, t)

print(ret)