228. Summary Ranges

You are given a sorted unique integer array nums.

A range [a,b] is the set of all integers from a to b (inclusive).

Return the smallest sorted list of ranges that cover all the numbers in the array exactly. That is, each element of nums is covered by exactly one of the ranges, and there is no integer x such that x is in one of the ranges but not in nums.

Each range [a,b] in the list should be output as:

"a->b" if a != b
"a" if a == b

Example 1:

Input: nums = [0,1,2,4,5,7]
Output: ["0->2","4->5","7"]
Explanation: The ranges are:
[0,2] --> "0->2"
[4,5] --> "4->5"
[7,7] --> "7"

Example 2:

Input: nums = [0,2,3,4,6,8,9]
Output: ["0","2->4","6","8->9"]
Explanation: The ranges are:
[0,0] --> "0"
[2,4] --> "2->4"
[6,6] --> "6"
[8,9] --> "8->9"

Constraints:

• 0 <= nums.length <= 20
• -2^31 <= nums[i] <= 2^31 - 1
• All the values of nums are unique.
• nums is sorted in ascending order

Code

C++ #01

class Solution
{
public:
    vector<string> summaryRanges(vector<int> &nums)
    {
        // fiding continuous number
        int lp = 0, rp = 1;

        vector<string> ans;
        if (nums.size() == 1)
        {
            ans.push_back(to_string(nums[0]));
            return ans;
        }

        while (nums.size() >= rp)
        { // continuous
            if (nums[rp - 1] + 1 == nums[rp] || nums[lp] == nums[rp])
            {
                rp++;
            }
            else
            { // nor not
                string temp;
                temp = (lp == rp - 1) ? to_string(nums[lp]) : to_string(nums[lp]) + "->" + to_string(nums[rp - 1]);
                ans.push_back(temp);
                lp = rp;
            }
            if (rp == nums.size())
            {
                string temp;
                temp = (lp == rp - 1) ? to_string(nums[lp]) : to_string(nums[lp]) + "->" + to_string(nums[rp - 1]);
                ans.push_back(temp);
                rp++;
            }
        }
        return ans;
    }
};

C++ #02 - Code Refactoring

class Solution
{

private:
    string convert(vector<int> &nums, int lp, int rp){
        if(lp == rp - 1) {    
            return to_string(nums[lp]);
        }
        else{
            return to_string(nums[lp]) + "->" + to_string(nums[rp - 1]);
        }
    }
    
public:
    vector<string> summaryRanges(vector<int> &nums)
    {
        // fiding continuous number
        int lp = 0, rp = 1;
        vector<string> ans;
        
        if (nums.size() == 0){
            return ans;
        }

        while (true)
        {   //base case
            if (rp >= nums.size())
            {
                ans.push_back(convert(nums, lp, rp));
                return ans;
            }
            //continuous
            if (nums[rp - 1] + 1 == nums[rp])
            {
                rp++;
            }
            // or not
            else
            { // or not // else문에서 계속 반복되다가 oveflow 발생
                ans.push_back(convert(nums, lp, rp));
                lp = rp;
                rp++;
            }
        }
    }
};