740. Delete and Earn

难度: Medium

题目描述

You are given an integer array nums. You want to maximize the number of points you get by performing the following operation any number of times:

• Pick any nums[i] and delete it to earn nums[i] points. Afterwards, you must delete every element equal to nums[i] - 1 and every element equal to nums[i] + 1.

Return the maximum number of points you can earn by applying the above operation some number of times.

 

Example 1:

Input: nums = [3,4,2]
Output: 6
Explanation: You can perform the following operations:
- Delete 4 to earn 4 points. Consequently, 3 is also deleted. nums = [2].
- Delete 2 to earn 2 points. nums = [].
You earn a total of 6 points.

Example 2:

Input: nums = [2,2,3,3,3,4]
Output: 9
Explanation: You can perform the following operations:
- Delete a 3 to earn 3 points. All 2's and 4's are also deleted. nums = [3,3].
- Delete a 3 again to earn 3 points. nums = [3].
- Delete a 3 once more to earn 3 points. nums = [].
You earn a total of 9 points.

 

Constraints:

• 1 <= nums.length <= 2 * 104
• 1 <= nums[i] <= 104

解题思路

代码实现

解决方案

java

class Solution {
    public int deleteAndEarn(int[] nums) {
        int n = nums.length;
        if (n == 1) {
            return nums[0];
        }
        int[] data = handleArray(nums);
        int[] dp = new int[data.length];
        dp[0] = data[0];
        dp[1] = Math.max(data[0], data[1]);
        for (int i = 2; i < data.length; i++) {
            dp[i] = Math.max(data[i] + dp[i - 2], dp[i - 1]);
        }
        return dp[data.length - 1];
    }

    public int[] handleArray(int[] nums) {
        Map<Integer, Integer> dataMap = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            if (dataMap.containsKey(nums[i])) {
                dataMap.put(nums[i], dataMap.get(nums[i]) + nums[i]);
            } else {
                dataMap.put(nums[i], nums[i]);
            }
        }
        Map<Integer, Integer> res = new TreeMap<>(dataMap);
        for(int i: dataMap.keySet()){
            if(!res.containsKey(i-1)){
                res.put(i-1,0);
            }
        }
        return res.values().stream().mapToInt(Integer::intValue).toArray();
    }


}