LeetCode - Delete and Earn

Question Definition

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].

  Java Solution

  public int deleteAndEarn(int[] nums) {
        int[] sums = new int[10001];
        // int take = 0, skip = 0;
        for (int num : nums) sums[num] += num;
        // for (int i = 0; i < 10001; ++i) {
        //     int takei = skip + sums[i];
        //     int skipi = Math.max(skip, take);
        //     take = takei; skip = skipi;
        // }
        // return Math.max(skip, take);
        for (int i = 2; i < 10001; ++i) {
            sums[i] = Math.max(sums[i - 1], sums[i - 2] + sums[i]);
        }
        return sums[10000];
    }