第274题(2020-08-07)：在排序数组中查找元素的第一个和最后一个位置 （腾讯、字节）

[qappleh]

No description provided.

[qappleh]

二分查找

let searchRange = function(nums, target) {
    return [leftSearch(nums, target), rightSearch(nums, target)]
}

let leftSearch = function(nums, target) {
    let low = 0, 
        high = nums.length - 1,
        mid
    while (low <= high) {
        mid = Math.floor((low+high)/2)
        if (nums[mid] < target) {
            low = mid + 1
        } else if (nums[mid] > target) {
            high = mid - 1
        } else if (nums[mid] === target) {
            // 这里不返回，继续收缩左侧边界
            high = mid - 1
        }
    }
    // 最后检查 low 是否越界或命中
    if (low >= nums.length || nums[low] != target)
        return -1
    return low
}


let rightSearch = function (nums, target) {
    let low = 0, 
        high = nums.length - 1,
        mid
    while (low <= high) {
        mid = Math.floor((low+high)/2)
        if (nums[mid] < target) {
            low = mid + 1
        } else if (nums[mid] > target) {
            high = mid - 1
        } else if (nums[mid] === target) {
            // 这里不返回，继续收缩右侧边界
            low = mid + 1
        }
    }
    // 最后检查 high 是否越界或命中
    if (high < 0 || nums[high] != target)
        return -1
    return high
}

复杂度分析：

• 时间复杂度：O(logn)
• 空间复杂度：O(1)

附赠leetcode地址：leetcode