1、原题
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
2、思路
3、代码
class Solution {
func search(_ nums: [Int], _ target: Int) -> Int {
// 先定义有序数组的两个边界，当前定义的是左闭右闭[left, right]
var left = 0
var right = nums.count - 1
// 所以下面的循环条件就是 <=
while left <= right {
// 初始化中间值，使用这种方式，防止大值溢出
let middle = left + ((right - left) >> 1)
if nums[middle] == target {
return middle
} else if nums[middle] < target {
left = middle + 1
} else {
right = middle - 1
}
}
// 目标值没有在原数组中，并且大于最右边界
return -1
}
}
