704. 二分查找

[Geekhyt]

原题链接

二分查找

理解二分算法可以参考：二分查找详解

// 左闭右闭区间
const search = function(nums, target) {
    let start = 0
    let end = nums.length - 1
    while (start <= end) {
        const mid = start + ((end - start) >> 1)
        if (nums[mid] === target) return mid

        if (nums[mid] < target) {
            start = mid + 1
        } else {
            end = mid - 1
        }
    }
    return -1
}

// 左闭右开区间
const search = function(nums, target) {
    let start = 0
    let end = nums.length
    while (start < end) {
        const mid = start + ((end - start) >> 1)
        if (nums[mid] === target) return mid

        if (nums[mid] < target) {
            start = mid + 1
        } else {
            end = mid
        }
    }
    return -1
}

• 时间复杂度：O(logn)
• 空间复杂度：O(1)