python 二分法查找

 

class Solution(object):
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        left, right = 0, len(nums) - 1

        while left <= right:

            mid = (left + right) // 2

            if nums[mid] == target:
                return mid

            if nums[left] <= nums[mid]:  # LHS is sorted
                if target >= nums[left] and target < nums[mid]:  # target is on LHS
                    right = mid - 1
                else:
                    left = mid + 1
            else:  # RHS is sorted
                if target <= nums[right] and target > nums[mid]:  # target is on RHS
                    left = mid + 1
                else:
                    right = mid - 1

        return -1
        
x=Solution()
print(x.search([4,7,8,9],9))