7/2 每日一題(兩組字串中取不同值)

 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.

class Solution:

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

        freq={}

        for i in t:

            freq[i]=freq.get(i,0)+1

            #避免KeyError,當Key不存在時 新增{key:0}

        for i in s:

            freq[i] -=1 #當循環結束 val==1的值 就是不同的key

        for key,val in freq.items():

            if val > 0:

                return key

-------------------------------法二

from collections import Counter

s='abcd'

t='abdcy'

c_s=Counter(s)

c_t=Counter(t)

print(c_s)

print(c_t)

print(c_t-c_s)

---------------------終端機

Counter({'a': 1, 'b': 1, 'c': 1, 'd': 1}) Counter({'a': 1, 'b': 1, 'd': 1, 'c': 1, 'y': 1}) Counter({'y': 1})