二分查找

class Solution:
    def search(self, nums: List[int], target: int) -> int:
        left=0
        right = len(nums)-1
        while left<=right:
            mid = left+(right-left)//2
            if nums[mid] == target:
                return mid
            elif nums[mid]<target:
                left =mid+1
            elif nums[mid]>target:
                right =mid-1
        return -1