题目描述：
Given a sorted array of integers, find the starting and ending position of a given target value.
Your algorithm's runtime complexity must be in the order of O(log n).
If the target is not found in the array, return [-1, -1].
For example,
Given [5, 7, 7, 8, 8, 10] and target value 8,
return [3, 4].
就是在排序的数组中找到一个区间的起始和终止边界索引。
思路：
1. 对于目标数target,在数组nums中使用二分查找到该值的一个索引i
2. 找到nums[i] < target的左边界，i∈[0,i), 找到nums[j] > target的右边界，j∈[i,n)
实现代码：
public class Solution {
public int[] SearchRange(int[] nums, int target)
{
if(target > nums[nums.Length - 1] || target < nums[0]){
return new int[2]{-1,-1};
}
var i = Array.BinarySearch<int>(nums,target);
if(i < 0){
return new int[2]{-1,-1};
}
var l = i;
var r = i;
while(l >= 0 && nums[l] == target){
l --;
}
while(r < nums.Length && nums[r] == target){
r++;
}
return new int[2]{l+1,r-1};
}
}