Find the Difference

Given two strings s and t which consist of only lowercase letters.

String t is generated by random shuffling string s and then add one more letter at a random position.

Find the letter that was added in t.

Example:

Input:
s = "abcd"
t = "abcde"
Output:
e
Explanation:
'e' is the letter that was added.

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        dict = {}
        for c in s:
            dict[c] = dict.get(c, 0) + 1
        for c in t:
            if not dict.get(c, 0):
                return c
            dict[c] -= 1