Given an array of integers nums which is sorted in ascending order, and an integer target, write a function to search target in nums. If target exists, then return its index. Otherwise, return -1.
You must write an algorithm with O(log n) runtime complexity.
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
Constraints:
1 <= nums.length <= 104
-104 < nums[i], target < 104
All the integers in nums are unique.
nums is sorted in ascending order.
https://leetcode.cn/problems/binary-search/description/
思路：二分查找
「二分查找」是利用数组的有序性，每轮缩窄一半的查找区间（即排除一半元素），直到找到目标值或查找区间为空时返回。
class Solution:def search(self, nums: List[int], target: int) -> int:i, j = 0, len(nums) - 1while i <= j:m = (i + j) // 2if nums[m] < target: i = m + 1elif nums[m] > target: j = m - 1else: return mreturn -1