old_contents: # Time:  O(logn)
  # Space: O(1)
  
  # A peak element is an element that is greater than its neighbors.
  # 
  # Given an input array where num[i] != num[i+1],
  # find a peak element and return its index.
  # 
  # The array may contain multiple peaks, in that case 
  # return the index to any one of the peaks is fine.
  # 
  # You may imagine that num[-1] = num[n] = -infinite.
  # 
  # For example, in array [1, 2, 3, 1], 3 is a peak element
  # and your function should return the index number 2.
  #
  # Note:
  # Your solution should be in logarithmic complexity.
  
  
  class Solution(object):
      def findPeakElement(self, nums):
          """
          :type nums: List[int]
          :rtype: int
          """
          left, right = 0, len(nums) - 1
          
          while left < right:
              mid = left + (right - left) / 2
              if (mid == 0 or nums[mid - 1] < nums[mid]) and \
                 (mid + 1 == len(nums) or nums[mid] > nums[mid + 1]):
                  return mid
              elif not (mid == 0 or nums[mid - 1] < nums[mid]):
                  right = mid
              else:
                  left = mid + 1
         
          return left
  
  
  if __name__ == "__main__":
     # print Solution().findPeakElement([1,2,1])
      print Solution().findPeakElement([1,2,3,1])
  
new_contents: # Time:  O(logn)
  # Space: O(1)
  
  # A peak element is an element that is greater than its neighbors.
  # 
  # Given an input array where num[i] != num[i+1],
  # find a peak element and return its index.
  # 
  # The array may contain multiple peaks, in that case 
  # return the index to any one of the peaks is fine.
  # 
  # You may imagine that num[-1] = num[n] = -infinite.
  # 
  # For example, in array [1, 2, 3, 1], 3 is a peak element
  # and your function should return the index number 2.
  #
  # Note:
  # Your solution should be in logarithmic complexity.
  
  
  class Solution(object):
      def findPeakElement(self, nums):
          """
          :type nums: List[int]
          :rtype: int
          """
          left, right = 0, len(nums) - 1
          
          while left < right:
              mid = left + (right - left) / 2
              if (mid == 0 or nums[mid - 1] < nums[mid]) and \
                 (mid + 1 == len(nums) or nums[mid] > nums[mid + 1]):
                  return mid
              elif not (mid == 0 or nums[mid - 1] < nums[mid]):
                  right = mid
              else:
                  left = mid + 1
         
          return left
      
      def findPeakElement2(self, nums):
          """
          :type nums: List[int]
          :rtype: int
          """
          left, right = 0, len(nums) - 1
          
          while left < right:
              mid = left + (right - left) / 2
              if nums[mid] > nums[mid + 1]:
                  right = mid
              else:
                  left = mid + 1
         
          return left
  
  if __name__ == "__main__":
     # print Solution().findPeakElement([1,2,1])
      print Solution().findPeakElement([1,2,3,1])
  
subject: Update find-peak-element.py