1) Given an integer, 看这个integer是否是对称的(palindrome), 就是正着和倒着是否都一样
2) Array of non-negative integers. One number appears odd number of times, all the others appear even number of times. Find the number that appears odd number of times.
3) What's the difference between method overwriting and method overloading?
4) What's the difference between interface/abstract class?
5) Design question. Design a system for a building with several elevators.
6) SQL question. Given a table with 2 columns, company name, revenue. Write a sql to get all the revenue for each company.
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