704.Binary Search（二分查找）

Given a sorted (in ascending order) integer array nums of n elements and a target value, write a function to search target in nums. If target exists, then return its index, otherwise return -1.

Example 1:

Input: nums = [-1,0,3,5,9,12], target = 9
Output: 4
Explanation: 9 exists in nums and its index is 4

Example 2:

Input: nums = [-1,0,3,5,9,12], target = 2
Output: -1
Explanation: 2 does not exist in nums so return -1

Note:

1. You may assume that all elements in nums are unique.
2. n will be in the range [1, 10000].
3. The value of each element in nums will be in the range [-9999, 9999].

Solution1:

class Solution:
    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 - left)//2 #rather than use mid=(left+right)//2
            if nums[mid]==target:
                return mid
            if nums[mid]<target:
                left = mid + 1
            else:
                right = mid - 1
        return -1

Solution2:

class Solution:
    def search(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: int
        """
        try:
            return nums.index(target)
        except:
            return -1