LeetCode 34 查找元素

class Solution {
    public:
        vector<int> searchRange(vector<int>& nums, int target) {
            int n=nums.size();
            vector<int> ans;
            ans={0,0};
            
            if(nums.size()==0){
                ans[0]=-1;
                ans[1]=-1;
                return ans;
            }
            int rightB=getRight(nums,target);
            int leftB=getLeft(nums,target);
            if(rightB==-2||leftB==-2){
                return {-1,-1};
            }
            if((rightB-leftB)>1){
                return {leftB+1,rightB-1};

            }else{
                return {-1,-1};
            }
        }

    private:
        int getRight(vector<int>& nums, int target){
            int l=0;
            int r=nums.size()-1;
            int mid=0;
            int rightB=-2;
            while(l<=r){
                mid=(l+r)/2;
                if(nums[mid]>target){
                    r=mid-1;
                }else if(nums[mid]<=target){
                    l=mid+1;
                    rightB=l;
                }
            }
            return rightB;
        }
        int getLeft(vector<int>& nums, int target){
            int l=0;
            int r=nums.size()-1;
            int mid=0;
            int leftB=-2;
            while(l<=r){
                mid=(l+r)/2;
                if(nums[mid]>=target){
                    r=mid-1;
                    leftB=r;
                }else if(nums[mid]<target){
                    l=mid+1;

                }
            }
            return leftB;
        }
    };

参考代码随想录二分法求边界的方法