[Google] LeetCode 2178 Maximum Split of Positive Even Integers 贪心

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): (12), (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.

Solution

为了求得最长长度的答案，显然应该从最小的偶数 \(st=2\) 开始，每次 \(+2\). 但是如果 \(f-st\le st\) 说明不能再减了，因为比 \(st\) 小的偶数都已经用过了，所以此时直接将 \(f\) 加入答案即可。

点击查看代码

class Solution {
private:
    vector<long long> ans;
public:
    vector<long long> maximumEvenSplit(long long finalSum) {
        if(finalSum%2)return ans;
        long long st = 2;
        while(finalSum){
            if(finalSum-st<=st){
                ans.push_back(finalSum);break;
            }
            ans.push_back(st);
            finalSum-=st; st+=2;
        }
        return ans;
    }
};