leetcode-389.Find the Difference

2017-05-22

题目传送门:Find the Difference

题意:给两个字符串s,t t串是由s串中的字母组成，并额外添加了1个或多个字母，找出这些额外的字母.

思路:把t串扔set里先去重，然后构造两个个字典，key为set里的字母，分别统计s,t的字母的次数，然后遍历set输出字母出现次数之差即可.

题目描述:

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:

Explanation:

‘e’ is the letter that was added.

Python代码:

class Solution(object):
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        ms = {}
        mt = {}
        ans = "";
        for key in set(t) :
            ms.setdefault(key,0) 
            mt.setdefault(key,0)
            
        for var in s :
            ms[var]+=1
            
        for var in t :
            mt[var]+=1
        
        for var in set(t) :
            for num in range(0,mt[var]-ms[var]) :
                ans+=var
        
        return ans;