[LeetCode] Challenge log 389

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389. Find the Difference

Best solution is to use bitwise operation XOR: same ele will be cancel if xor twice.

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:

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Input:
s = "abcd"
t = "abcde"

Output:
e

Explanation:
'e' is the letter that was added.
Soulution:
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class Solution:
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        count = {}
        for i in s:
            if i not in count:
                count[i] = 1
            else:
                count[i] += 1
        for i in t:
            if i not in count:
                return i
            else:
                count[i] -= 1
        for key in count:
            if count[key] < 0: 
                return key
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class Solution:
    def findTheDifference(self, s, t):
        """
        :type s: str
        :type t: str
        :rtype: str
        """
        res = 0
        for i in s + t:
            res ^= ord(i)
        return chr(res)
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