# 二分查找
只能在升序的数组中使用
实现原理: 左右递减, 取中间下标进行匹配, 如果小于目标值, 左下标向右移动一位, 反之右下标项向左移动一位
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/**
* 二分查找
* @param {number[]} nums
* @param {number} target
* @returns number
*/
const binarySearch = (nums, target) => {
if (nums.length === 0) return -1
let left = 0,
right = nums.length - 1
while(left <= right) {
let mid = left + ((right - left) >> 1)
if (nums[mid] === target) {
return mid
} else if (nums[mid] < target) {
left = mid + 1
} else if(nums[mid] > target) {
right = mid - 1
}
}
return -1
}
// ---------- Test ---------
const nums = [1, 3, 6, 9, 10, 12, 16]
const target = 12
console.log(binarySearch(nums, target))
// 5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32