[Swift]LeetCode740. 删除与获得点数 | Delete and Earn

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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].

---

给定一个整数数组 nums ，你可以对它进行一些操作。

每次操作中，选择任意一个 nums[i] ，删除它并获得 nums[i] 的点数。之后，你必须删除每个等于 nums[i] - 1 或 nums[i] + 1 的元素。

开始你拥有 0 个点数。返回你能通过这些操作获得的最大点数。

示例 1:

输入: nums = [3, 4, 2]
输出: 6
解释: 
删除 4 来获得 4 个点数，因此 3 也被删除。
之后，删除 2 来获得 2 个点数。总共获得 6 个点数。

示例 2:

输入: nums = [2, 2, 3, 3, 3, 4]
输出: 9
解释: 
删除 3 来获得 3 个点数，接着要删除两个 2 和 4 。
之后，再次删除 3 获得 3 个点数，再次删除 3 获得 3 个点数。
总共获得 9 个点数。

注意:

• nums的长度最大为20000。
• 每个整数nums[i]的大小都在[1, 10000]范围内。

---

36ms

class Solution {
    func deleteAndEarn(_ nums: [Int]) -> Int {
        if nums.count == 0 {
            return 0
        }
        
        let maxN = nums.max()!
        var M  = [Int](repeating: 0, count: maxN + 1)
        var DP = [Int](repeating: 0, count: maxN + 1)
        
        for i in 0..<nums.count {
            M[nums[i]] += nums[i]
        }
        
        DP[0] = M[0]
        DP[1] = M[1]
        for i in 2..<M.count {
            DP[i] = max(DP[i - 2] + M[i],DP[i - 1])
        }
        
        return DP.last!
    }
}

---

40ms

class Solution {
    func deleteAndEarn(_ nums: [Int]) -> Int {
        let minValue = nums.min() ?? 0
        let maxValue = nums.max() ?? 0
        var dp = [Int](repeating: 0, count:maxValue + 1)
        for item in nums {
            dp[item] += item
        }

        if maxValue >= 2{
            for i in 2...maxValue {
                dp[i] = max(dp[i-2] + dp[i], dp[i-1])
            }        
        }

        return dp[maxValue]
    }
}

---

44ms

class Solution {
    func deleteAndEarn(_ nums: [Int]) -> Int {
        var counts = [Int: Int]()
        for num in nums {
            counts[num, default: 0] += 1
        }
        
        var prev = -1
        var avoid = 0
        var using = 0
        
        for num in counts.keys.sorted() {
            if num - 1 != prev {
                (avoid, using) = (max(avoid, using), num * counts[num]! + max(avoid, using))
            } else {
                (avoid, using) = (max(avoid, using), num * counts[num]! + avoid)
            }
            
            prev = num
        }        
        
        return max(avoid, using)
    }
}

---

Runtime: 52 ms

Memory Usage: 19.3 MB

class Solution {
    func deleteAndEarn(_ nums: [Int]) -> Int {
        var sums:[Int] = [Int](repeating:0,count:10001)
        for num in nums
        {
            sums[num] += num
        }
        for i in 2..<10001
        {
            sums[i] = max(sums[i - 1], sums[i - 2] + sums[i])
        }
        return sums[10000]
    }
}

---

92ms

class Solution {
    func deleteAndEarn(_ nums: [Int]) -> Int {
        if nums.count == 0 {
            return 0
        }
        if nums.count == 1 {
            return nums[0]
        }
        var numCount: [String: Int] = [:]
        var dp: [String : Int] = [:]
        var maxCount = 0
        for i in 0 ..< nums.count {
            if let a = numCount["\(nums[i])"] {
                numCount["\(nums[i])"] = a + 1
            }else {
                numCount["\(nums[i])"] = 1
            }
            if nums[i] > maxCount {
                maxCount = nums[i]
            }
        }
        dp["0"] = 0
        if let a = numCount["1"] {
            dp["1"] = a
        }else {
            dp["1"] = 0
        }
        for i in 2 ... maxCount {
            var a = 0
            if let e = dp["\(i - 1)"] {
                a = e
            }
            var b = 0
            var c = 0
            if let count = dp["\(i - 2)"] {
                c = count
            }
            if let count = numCount["\(i)"] {
                b = count * i + c
            }
            dp["\(i)"] = max(a, b)
        }
        return dp["\(maxCount)"]!
    }
}