求数组内异次出现的数

问题 1
'Given an array of integers, every element appears twice'' except for one. Find that single one.'''

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

问题 2
'Given an array of integers, every element appears 3 times'' except for one. Find that single one.'''

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