First&LastPositionElementSortedArray.cpp

class Solution {
public:
    
    int lowerBound(vector<int>& nums, int target)
    {
        int ans = -1;
        int s = 0, e = nums.size() - 1;
        
        while(s<=e)
        {
            int mid = s + (e-s)/2;
            if(nums[mid] == target)
            {
                ans = mid;
                e = mid - 1;
            }
            else if(nums[mid] > target)
                e = mid -1;
            else
                s = mid + 1;
        }
        return ans;
    }
    
    int upperBound(vector<int>& nums, int target)
    {
        int ans = -1;
        int s = 0, e = nums.size() - 1;
        
        while(s<=e)
        {
            int mid = s + (e-s)/2;
            if(nums[mid] == target)
            {
                ans = mid;
                s = mid + 1;
            }
            else if(nums[mid] > target)
                e = mid -1;
            else
                s = mid + 1;
        }
        return ans;
    }
    
    vector<int> searchRange(vector<int>& nums, int target) {
        int lower = lowerBound(nums, target);
        int upper = upperBound(nums, target);
        vector<int> ans;
        ans.push_back(lower);
        ans.push_back(upper);
        return ans;
    }
};