Given a non-empty array of integers, every element appears twice except for one. Find that single one.


Your algorithm should have a linear runtime complexity. Could you implement it without using extra memory?

Example 1:

Input: [2,2,1] Output: 1

Example 2:

Input: [4,1,2,1,2] Output: 4


We can use XOR property of two numbers, We already knows that a^a results to 0. Do XOR or all numbers, all duplicate numbers cancels each other.




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