p117 有序数组中查找数字的开始和结束下标(leetcode 34)

一：解题思路

Time:O(log(n)),Space:O(1)

二：完整代码示例 (C++版和Java版)

C++:

class Solution 
{
private:
    int binarySearchLastOne(vector<int>& nums, int target)
    {
        int low = 0, high = nums.size() - 1;
        while (low <= high)
        {
            int mid = low + (high-low) / 2;
            if (nums[mid] > target) high = mid - 1;
            else low = mid + 1;
        }

        return high;
    }
public:
    vector<int> searchRange(vector<int>& nums, int target) 
    {
        vector<int> ret = {-1,-1};
        if (nums.size() == 0) return ret;
        int end = binarySearchLastOne(nums,target);
        int start = binarySearchLastOne(nums,target-1)+1;
        if (start >= 0 && start <= end && end < nums.size())
            ret = {start,end};

        return ret;
    }
};

Java:

class Solution
    {
        private int binarySearchLastOne(int[] nums,int target)
        {
            int low=0;
            int high=nums.length-1;
            while(low<=high)
            {
                int mid=low+(high-low)/2;
                if(nums[mid]>target) high=mid-1;
                else low=mid+1;
            }
            
            return high;
        }

        public int[] searchRange(int[] nums, int target) 
        {
               if(nums==null || nums.length==0) return new int[]{-1,-1};
               int end=binarySearchLastOne(nums,target);
               int start=binarySearchLastOne(nums,target-1)+1;
               if(start>=0 && start<=end && end<nums.length)
                   return new int[]{start,end};
               return new int[]{-1,-1};
        }
    }