852. Peak Index in a Mountain Array

题目地址：https://leetcode.com/problems/peak-index-in-a-mountain-array/description/
大意：给一个峰值数列，返回峰值数的索引值

二分法

# 852. Peak Index in a Mountain Array
class Solution:
    def peakIndexInMountainArray(self, A):
        """
        :type A: List[int]
        :rtype: int
        """
        low = 0
        high = len(A) - 1
        while low < high:
            middle = (low + high) // 2
            if A[middle] < A[middle + 1]:
                low = middle +1
            else:
                high = middle
        return low

a = Solution()
print (a.peakIndexInMountainArray([0,1,0]))

答案中还给了线性查找的方法，有兴趣的可以看看：

线性查找

The mountain increases until it doesn't. The point at which it stops increasing is the peak.

class Solution(object):
    def peakIndexInMountainArray(self, A):
        for i in xrange(len(A)):
            if A[i] > A[i+1]:
                return i

注意：

• /除号python2和python3不同，middle = (low + high) // 2需要用两个/才能得到整数，要不然会有错误。
• xrang()的用法http://www.runoob.com/python/python-func-xrange.html
  
  
  
  

所有题目解题方法和答案代码地址：https://github.com/fredfeng0326/LeetCode