#
# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
# 如果目标值存在返回下标，否则返回 -1
# @param nums int整型一维数组 
# @param target int整型 
# @return int整型
#
class Solution:
    def search(self , nums , target ):

        # write code here
        left, right = 0, len(nums)-1
        while left <= right:
            mid = (left+right)//2
            if nums[left] == target:
                return left
            elif nums[mid] > target:
                right = mid - 1
            elif nums[mid] < target:
                left = mid + 1
            else:
                right = mid
                left += 1
        return -1

注意返回左边就好了