389 find the difference
389. Find the Difference
题目: https://leetcode.com/problems/find-the-difference/
难度:
Easy
用个字典来记录，把s加进去，把t减掉，最后剩下那个要么个数为1，要么个数为-1
class Solution(object):
def findTheDifference(self, s, t):
"""
:type s: str
:type t: str
:rtype: str
"""
res = {}
for i in s:
res[i] = res.get(i, 0) + 1
for j in t:
res[j] = res.get(j, 0) - 1
for key in res:
if abs(res[key]) == 1: # 这里用 abs 是因为新增加的那个字母在 s 中可能未出现过
return key
还有一个简单的方法
class Solution(object):
def findTheDifference(self, s, t):
"""
:type s: str
:type t: str
:rtype: str
"""
from collections import Counter
return list((Counter(t) - Counter(s)).keys()).pop()
