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].

給定一個整數數組 nums ，你可以對它進行一些操作。

每次操作中，選擇任意一個 nums[i] ，刪除它並獲得 nums[i] 的點數。之後，你必須刪除每個等於 nums[i] - 1 或 nums[i] + 1 的元素。

開始你擁有 0 個點數。返回你能通過這些操作獲得的最大點數。

示例 1:

輸入: nums = [3, 4, 2]
輸出: 6
解釋: 
刪除 4 來獲得 4 個點數，因此 3 也被刪除。
之後，刪除 2 來獲得 2 個點數。總共獲得 6 個點數。

示例 2:

輸入: nums = [2, 2, 3, 3, 3, 4]
輸出: 9
解釋: 
刪除 3 來獲得 3 個點數，接著要刪除兩個 2 和 4 。
之後，再次刪除 3 獲得 3 個點數，再次刪除 3 獲得 3 個點數。
總共獲得 9 個點數。

註意:

• nums的長度最大為20000。
• 每個整數nums[i]的大小都在[1, 10000]範圍內。

36ms

 1 class Solution {
 2     func deleteAndEarn(_ nums: [Int]) -> Int {
 3         if nums.count == 0 {
 4             return 0
 5         }
 6         
 7         let maxN = nums.max()!
 8         var M  = [Int](repeating: 0, count: maxN + 1)
 9         var DP = [Int](repeating: 0, count: maxN + 1)
10         
11         for i in 0..<nums.count {
12             M[nums[i]] += nums[i]
13         }
14         
15         DP[0] = M[0]
16         DP[1] = M[1]
17         for i in 2..<M.count {
18             DP[i] = max(DP[i - 2] + M[i],DP[i - 1])
19         }
20         
21         return DP.last!
22     }
23 }

40ms

 1 class Solution {
 2     func deleteAndEarn(_ nums: [Int]) -> Int {
 3         let minValue = nums.min() ?? 0
 4         let maxValue = nums.max() ?? 0
 5         var dp = [Int](repeating: 0, count:maxValue + 1)
 6         for item in nums {
 7             dp[item] += item
 8         }
 9 
10         if maxValue >= 2{
11             for i in 2...maxValue {
12                 dp[i] = max(dp[i-2] + dp[i], dp[i-1])
13             }        
14         }
15 
16         return dp[maxValue]
17     }
18 }

44ms

 1 class Solution {
 2     func deleteAndEarn(_ nums: [Int]) -> Int {
 3         var counts = [Int: Int]()
 4         for num in nums {
 5             counts[num, default: 0] += 1
 6         }
 7         
 8         var prev = -1
 9         var avoid = 0
10         var using = 0
11         
12         for num in counts.keys.sorted() {
13             if num - 1 != prev {
14                 (avoid, using) = (max(avoid, using), num * counts[num]! + max(avoid, using))
15             } else {
16                 (avoid, using) = (max(avoid, using), num * counts[num]! + avoid)
17             }
18             
19             prev = num
20         }        
21         
22         return max(avoid, using)
23     }
24 }

 1 class Solution {
 2     func deleteAndEarn(_ nums: [Int]) -> Int {
 3         var sums:[Int] = [Int](repeating:0,count:10001)
 4         for num in nums
 5         {
 6             sums[num] += num
 7         }
 8         for i in 2..<10001
 9         {
10             sums[i] = max(sums[i - 1], sums[i - 2] + sums[i])
11         }
12         return sums[10000]
13     }
14 }

92ms

 1 class Solution {
 2     func deleteAndEarn(_ nums: [Int]) -> Int {
 3         if nums.count == 0 {
 4             return 0
 5         }
 6         if nums.count == 1 {
 7             return nums[0]
 8         }
 9         var numCount: [String: Int] = [:]
10         var dp: [String : Int] = [:]
11         var maxCount = 0
12         for i in 0 ..< nums.count {
13             if let a = numCount["\(nums[i])"] {
14                 numCount["\(nums[i])"] = a + 1
15             }else {
16                 numCount["\(nums[i])"] = 1
17             }
18             if nums[i] > maxCount {
19                 maxCount = nums[i]
20             }
21         }
22         dp["0"] = 0
23         if let a = numCount["1"] {
24             dp["1"] = a
25         }else {
26             dp["1"] = 0
27         }
28         for i in 2 ... maxCount {
29             var a = 0
30             if let e = dp["\(i - 1)"] {
31                 a = e
32             }
33             var b = 0
34             var c = 0
35             if let count = dp["\(i - 2)"] {
36                 c = count
37             }
38             if let count = numCount["\(i)"] {
39                 b = count * i + c
40             }
41             dp["\(i)"] = max(a, b)
42         }
43         return dp["\(maxCount)"]!
44     }
45 }

[Swift]LeetCode740. 刪除與獲得點數 | Delete and Earn