2829. Determine the Minimum Sum of a k-avoiding Array

Problem Statement

You are given two integers, n and k.

An array of distinct positive integers is called a k-avoiding array if there does not exist any pair of distinct elements that sum to k.

Return the minimum possible sum of a k-avoiding array of length n.

Example 1:

Input: n = 5, k = 4
Output: 18
Explanation: Consider the k-avoiding array [1,2,4,5,6], which has a sum of 18.
It can be proven that there is no k-avoiding array with a sum less than 18.

Example 2:

Input: n = 2, k = 6
Output: 3
Explanation: We can construct the array [1,2], which has a sum of 3.
It can be proven that there is no k-avoiding array with a sum less than 3.

Constraints:

1 <= n, k <= 50

Intuition

Basically,
We want minimum sum
So start from 1 and go along

Store the alternate sum in hash set 
Eg- k = 6
Take 1, Store 5 in map so you can skip that number ahead

Links

2829. Determine the Minimum Sum of a k-avoiding Array

Video Links

Approach 1:

C++

class Solution {
public:
    int minimumSum(int n, int k) {
        int ans = 0;
        unordered_map<int,int> mp;
        int i=1;

        while(n){
            if(mp.find(i) == mp.end()){
                ans += i;
                mp[k-i] = 1;
                n--;
            }
            i++;
        }

        return ans;
    }
};

Approach 2:

C++

Approach 3:

C++

Approach 4:

C++