389. Find the Difference

Easy

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You are given two strings s and t.

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

Return the letter that was added to t.

Example 1:

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

Example 2:

Input: s = "", t = "y"
Output: "y"

Constraints:

• 0 <= s.length <= 1000

• t.length == s.length + 1

• s and t consist of lowercase English letters.

from collections import defaultdict
class Solution:
    def findTheDifference(self, s: str, t: str) -> str:
        # one more letter at a random position
        # This line in question seems wrong because it doesn't allow test case beyond one char diff
        result = ''
        hash1 = self.get_hash(s)
        hash2 = self.get_hash(t)
        for key in hash2.keys():
            if key not in hash1:
                result = result + key*hash2[key]
            elif hash2[key] != hash1[key]:
                result = result + key*(hash2[key]-hash1[key])
        return result
    
    def get_hash(self, s:str):
        d = defaultdict(int)
        for char in s:
            d[char] += 1
        return d