2178. Maximum Split of Positive Even Integers

You are given an integer finalSum. Split it into a sum of a maximum number of unique positive even integers.

• For example, given finalSum = 12, the following splits are valid (unique positive even integers summing up to finalSum): (2 + 10), (2 + 4 + 6), and (4 + 8). Among them, (2 + 4 + 6) contains the maximum number of integers. Note that finalSum cannot be split into (2 + 2 + 4 + 4) as all the numbers should be unique.

Return a list of integers that represent a valid split containing a maximum number of integers. If no valid split exists for finalSum, return an empty list. You may return the integers in any order.

class Solution {
public:
    vector<long long> maximumEvenSplit(long long finalSum) {
        if(finalSum == 0 or (finalSum & 1)) return {};
        long long sum = 0, start = 2;
        vector<long long> res;
        while(sum + start <= finalSum) {
            res.push_back(start);
            sum += start;
            start += 2;
        }
        if(sum == finalSum)
            return res;
        long long req = finalSum - sum;
        res.back() += req;
        return res;
    }
};