LeetCode 740. Delete and Earn

740. Delete and Earn

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

	class Solution {
	public:
	// Point: DP on input integer range!
	int deleteAndEarn(vector<int>& nums) {
	int nmax = 1e4 + 1;
	map<int, int> cnt;
	for(auto x: nums) cnt[x]++;
	vector<int> dp(nmax + 1);
	dp[0] = 0;
	dp[1] = cnt[1];
	for(int i = 2; i < nmax; i++){
	dp[i] = max(dp[i-1], dp[i-2] + cnt[i] * i);
	}
	return dp[nmax - 1];
	}
	};

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