[leetcode]888. Fair Candy Swap

Description

Alice and Bob have candy bars of different sizes: A[i] is the size of the i-th bar of candy that Alice has, and B[j] is the size of the j-th bar of candy that Bob has.

Since they are friends, they would like to exchange one candy bar each so that after the exchange, they both have the same total amount of candy. (The total amount of candy a person has is the sum of the sizes of candy bars they have.)

Return an integer array ans where ans[0] is the size of the candy bar that Alice must exchange, and ans[1] is the size of the candy bar that Bob must exchange.

If there are multiple answers, you may return any one of them. It is guaranteed an answer exists.

Example 1:

Input: A = [1,1], B = [2,2]
Output: [1,2]

Example 2:

Input: A = [1,2], B = [2,3]
Output: [1,2]

Example 3:

Input: A = [2], B = [1,3]
Output: [2,3]

Example 4:

Input: A = [1,2,5], B = [2,4]
Output: [5,4]

Note:

• 1 <= A.length <= 10000
• 1 <= B.length <= 10000
• 1 <= A[i] <= 100000
• 1 <= B[i] <= 100000
• It is guaranteed that Alice and Bob have different total amounts of candy.
• It is guaranteed there exists an answer.

分析

题目的意思是：Alice 和 Bob分别有不同数量的糖，现在他们只能交换一次使得他们的糖的数量相等，意思很明确。我也没做出来，这是一个数学题目，看了答案恍然大悟，怪自己不愿意动笔了。

通过表达式可以得到只需要遍历找到满足条件的x，y就行了

代码

class Solution:
    def fairCandySwap(self, A: List[int], B: List[int]) -> List[int]:
        Sa=sum(A)
        Sb=sum(B)
        setB=set(B)
        for item in A:
            res=(Sb-Sa)/2+item
            if(res in setB):
                return [item,int(res)]
        

参考文献

​​[LeetCode] Approach 1: Solve the Equation​​