5265. Greatest Sum Divisible by Three

Given an array nums of integers, we need to find the maximum possible sum of elements of the array such that it is divisible by three.

 

Example 1:

Input: nums = [3,6,5,1,8]
Output: 18
Explanation: Pick numbers 3, 6, 1 and 8 their sum is 18 (maximum sum divisible by 3).
Example 2:

Input: nums = [4]
Output: 0
Explanation: Since 4 is not divisible by 3, do not pick any number.
Example 3:

Input: nums = [1,2,3,4,4]
Output: 12
Explanation: Pick numbers 1, 3, 4 and 4 their sum is 12 (maximum sum divisible by 3).
 

Constraints:

1 <= nums.length <= 4 * 10^4
1 <= nums[i] <= 10^4

来源：力扣（LeetCode）
链接：https://leetcode-cn.com/problems/greatest-sum-divisible-by-three
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动态规划，貌似我只会做这一道题，，，， ，

反正这个数被三除只有三种情况 整除 余1 余2，so只记录这三种情况最大和一直更新就OK啦

class Solution {
public:
    int maxSumDivThree(vector<int>& nums) {
        int one=0;
        int two=0;
        int three=0;
        for(int i=0;i<nums.size();i++){
            int a=nums[i]+one;
            int b=nums[i]+two;
            int c=nums[i]+three;
            if(a%3==0){
                if(a>three){
                    three=a;
                }
            }else if(a%3==1){
                if(a>one){
                    one=a;
                }
            }else if(a%3==2){
                if(a>two){
                    two=a;
                }
            }
            if(b%3==0){
                if(b>three){
                    three=b;
                }
            }else if(b%3==1){
                if(b>one){
                    one=b;
                }
            }else if(b%3==2){
                if(b>two){
                    two=b;
                }
            }
            if(c%3==0){
                if(c>three){
                    three=c;
                }
            }else if(c%3==1){
                if(c>one){
                    one=c;
                }
            }else if(c%3==2){
                if(c>two){
                    two=c;
                }
            }
            //cout<<one<<" "<<two<<" "<<three<<endl;
        }
        return three;
    }
};