34. 在排序数组中查找元素的第一个和最后一个位置（算法200题-48）

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var searchRange = function (nums, target) {
  if (!nums.length) return [-1, -1]
  let l = 0,
    r = nums.length - 1,
    mid = 0
  while (l <= r) {
    mid = Math.floor(l + (r - l) / 2)
    if (nums[mid] === target) {
      let i = mid - 1
          j = mid + 1
      while (nums[i] === target) {
        i--
      }
      while (nums[j] === target) {
        j++
      }
      return [i + 1, j - 1]
    }
    if (nums[mid] > target) {
      r = mid - 1
    } else {
      l = mid + 1
    }
  }
  return [-1, -1]
};