Half and Half 类型题
二分法的精髓在于判断目标值在前半区间还是后半区间，Half and Half类型难点在不能一次判断，可能需要一次以上的判断条件。
Maximum Number in Mountain Sequence
Given a mountain sequence of n integers which increase firstly and then decrease, find the mountain top.
nums = [1, 2, 4, 8, 6, 3] return 8 Given nums = [10, 9, 8, 7], return 10原文：http://www.cnblogs.com/yidansheng/p/7675356.html