Search for a range

class Solution {
public:
    int getfirst(vector<int>& nums,int low,int high,int target)
    {
        while(low<=high)
        {
            int mid=(low+high)/2;
            if(nums[mid]==target)
            {
                if(mid==0||nums[mid-1]!=target)
                    return mid;
                else
                    high=mid-1;
            }
            else if(nums[mid]>target)
                high=mid-1;
            else
                low=mid+1;
        }
        return -1;
    }
    
    int getlast(vector<int>& nums,int low,int high,int target)
    {
        while(low<=high)
        {
            int mid=(low+high)/2;
            if(nums[mid]==target)
            {
                if(mid==nums.size()-1||nums[mid+1]!=target)
                    return mid;
                else
                    low=mid+1;
            }
            else if(nums[mid]>target)
                high=mid-1;
            else
                low=mid+1;
        }
        return -1;
    }
    vector<int> searchRange(vector<int>& nums, int target) {
        vector<int> result(2,-1);
        if(nums.size()==0)
            return result;
        int low=0;
        int high=nums.size()-1;
        while(low<=high)
        {
            int mid=(low+high)/2;
            if(nums[mid]==target)
            {
                if(mid-1>=0&&nums[mid-1]==target)
                {
                    int l=getfirst(nums,low,mid-1,target);
                    result[0]=l;
                }
                else
                    result[0]=mid;
                if(mid+1<nums.size()&&nums[mid+1]==target)
                {
                    int r=getlast(nums,mid+1,high,target);
                    result[1]=r;
                }
                else
                    result[1]=mid;
                break;
            }
            else if(nums[mid]>target)
                high=mid-1;
            else
                low=mid+1;
        }
        return result;
        
    }
};

用二分查找法，分别查找重复数字的第一个位置和最后一个位置。

注意数组的下标范围，