740. Delete and Earn

#week14

Given an array nums of integers, you can perform operations on the array.

In each operation, you pick any nums[i] and delete it to earn nums[i] points. After, you must delete every element equal to nums[i] - 1 or nums[i] + 1.

You start with 0 points. Return the maximum number of points you can earn by applying such operations.

Example 1:

Input: nums = [3, 4, 2]
Output: 6
Explanation: 
Delete 4 to earn 4 points, consequently 3 is also deleted.
Then, delete 2 to earn 2 points. 6 total points are earned.

 

Example 2:

Input: nums = [2, 2, 3, 3, 3, 4]
Output: 9
Explanation: 
Delete 3 to earn 3 points, deleting both 2's and the 4.
Then, delete 3 again to earn 3 points, and 3 again to earn 3 points.
9 total points are earned.

 

Note:

• The length of nums is at most 20000.
• Each element nums[i] is an integer in the range [1, 10000].

题解：

class Solution {
public:
    int deleteAndEarn(vector<int>& nums) {
        int n = 10001;
        vector<int> values(n, 0);
        for (int num : nums)
            values[num] += num;

        int take = 0, skip = 0;
        for (int i = 0; i < n; i++) {
            int takei = skip + values[i];
            int skipi = max(skip, take);
            take = takei;
            skip = skipi;
        }
        return max(take, skip);
    }
};