34. Search for a Range

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 ofO(logn).

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].

二分查找的变形：

1、没有找到返回[-1, -1]

2、只存在1个返回[pos, pos]

3、存在多个，返回端点[leftPos, rightPos]

#include 
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看，这个时间，估计得有更高效的算法了。