【LeetCode】704. Binary Search

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704. Binary Search

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].

解題思路：

（1）二分查找

class Solution:
    def search(self, nums: List[int], target: int) -> int:

        if nums is None or len(nums) == 0:
            return -1

        low = 0
        high = len(nums) - 1

        while low <= high:
            mid = (low + high) // 2

            if nums[mid] == target:
                return mid
            elif nums[mid] < target:
                low = mid + 1
            else:
                high = mid - 1

        return -1