题型分类：数组中的二分查找
三种情况：
情况一：target在数组范围的右边或者左边，例如数组{3,4,5}，target为2或者数组{3,4,5}，target为6，此时应该返回{-1,-1}
情况二：target在数组范围中，且数组中不存在target，例如数组{3,6,7}，target为5，此时应该返回{-1,-1}
情况三：target在数组范围中，且数组中存在target，例如数组{3,6,7}，target为6，此时应该返回{1,1}
class Solution {
public:
int getRightBorder(vector<int>&nums,int target){
int left = 0;
int right = nums.size()-1;
int rightBorder = -2;
while(left<=right){
int middle = left+(right-left)/2;
if(nums[middle]>target){
right = middle-1;
}else{
left = middle+1;
rightBorder = left;
}
}
return rightBorder;
}
int getLeftBorder(vector<int>&nums,int target){
int left = 0;
int right = nums.size()-1;
int leftBorder = -2;
while(left<=right){
int middle = left+(right-left)/2;
if(nums[middle]>=target){
right = middle-1;
leftBorder = right;
}else{
left = middle+1;
}
}
return leftBorder;
}
vector<int> searchRange(vector<int>& nums, int target) {
int leftBorder = getLeftBorder(nums,target);
int rightBorder = getRightBorder(nums,target);
if(leftBorder == -2 || rightBorder ==-2) return {-1,-1};
if(rightBorder - leftBorder > 1) return {leftBorder+1,rightBorder-1};
return {-1,-1};
}
};