Leetcode34在排序数组中查找元素的第一个和最后一个位置(二分法求解)

/**
 \* @param {number[]} nums
 \* @param {number} target
 \* @return {number[]}
 */
var searchRange = function(nums, target) {
  let left = 0
  let right = nums.length
  let center = false
  while(left < right){
•    let mid = Math.floor(left + (right - left)/2)
•    if(nums[mid] < target){
•      left = mid + 1
•    }else if(nums[mid] > target){
•      right = mid
•    }else{
•      center = mid
•      left = mid
•      right = mid
•      break
•    }
  }
  if(center === false){
•    return [-1,-1]
  }else{
•    while(nums[left] == target){
•      left--
•    }
•    while(nums[right] == target){
•      right++
•    }
•    return [left+1,right-1]
  }
};