[Swift]LeetCode712. 兩個字符串的最小ASCII刪除和 | Minimum ASCII Delete Sum for Two Strings

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Given two strings s1, s2, find the lowest ASCII sum of deleted characters to make two strings equal.

Example 1:

Input: s1 = "sea", s2 = "eat"
Output: 231
Explanation: Deleting "s" from "sea" adds the ASCII value of "s" (115) to the sum.
Deleting "t" from "eat" adds 116 to the sum.
At the end, both strings are equal, and 115 + 116 = 231 is the minimum sum possible to achieve this.

Example 2:

Input: s1 = "delete", s2 = "leet"
Output: 403
Explanation: Deleting "dee" from "delete" to turn the string into "let",
adds 100[d]+101[e]+101[e] to the sum.  Deleting "e" from "leet" adds 101[e] to the sum.
At the end, both strings are equal to "let", and the answer is 100+101+101+101 = 403.
If instead we turned both strings into "lee" or "eet", we would get answers of 433 or 417, which are higher.

Note:

• 0 < s1.length, s2.length <= 1000.
• All elements of each string will have an ASCII value in [97, 122].

---

給定兩個字符串s1, s2，找到使兩個字符串相等所需刪除字符的ASCII值的最小和。

示例 1:

輸入: s1 = "sea", s2 = "eat"
輸出: 231
解釋: 在 "sea" 中刪除 "s" 並將 "s" 的值(115)加入總和。
在 "eat" 中刪除 "t" 並將 116 加入總和。
結束時，兩個字符串相等，115 + 116 = 231 就是符合條件的最小和。

示例 2:

輸入: s1 = "delete", s2 = "leet"
輸出: 403
解釋: 在 "delete" 中刪除 "dee" 字符串變成 "let"，
將 100[d]+101[e]+101[e] 加入總和。在 "leet" 中刪除 "e" 將 101[e] 加入總和。
結束時，兩個字符串都等於 "let"，結果即爲 100+101+101+101 = 403 。
若是改成將兩個字符串轉換爲 "lee" 或 "eet"，咱們會獲得 433 或 417 的結果，比答案更大。

注意:

• 0 < s1.length, s2.length <= 1000。
• 全部字符串中的字符ASCII值在[97, 122]之間。

---

Runtime: 196 ms

Memory Usage: 20 MB

 1 class Solution {
 2     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 3         var arr1:[Character] = Array(s1)
 4         var arr2:[Character] = Array(s2)
 5         var nums1:[Int] = arr1.map{$0.ascii}
 6         var nums2:[Int] = arr2.map{$0.ascii}
 7         var m:Int = s1.count
 8         var n:Int = s2.count
 9         var dp:[[Int]] = [[Int]](repeating:[Int](repeating:0,count:n + 1),count:m + 1)
10         for i in 1...m
11         {
12             for j in 1...n
13             {
14                 if arr1[i - 1] == arr2[j - 1]
15                 {
16                     dp[i][j] = dp[i - 1][j - 1] + nums1[i - 1]
17                 }
18                 else
19                 {
20                     dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
21                 }
22             }
23         }
24         var sum1:Int = nums1.reduce(0,+)
25         var sum2:Int = nums2.reduce(0,+)
26         return sum1 + sum2 - 2 * dp[m][n]
27     }
28 }
29 
30 //Character擴展 
31 extension Character  
32 {  
33   //Character轉ASCII整數值(定義小寫爲整數值)
34    var ascii: Int {
35        get {
36            return Int(self.unicodeScalars.first?.value ?? 0)
37        }       
38     }    
39 }

---

200ms

 1 final class Solution {
 2     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 3         let s1 = Array(s1.utf8).map(Int.init)
 4         let s2 = Array(s2.utf8).map(Int.init)
 5         var dp = [[Int]](repeating: Array(repeating: 0, count: s2.count &+ 1), count: s1.count &+ 1)
 6         
 7         for i in 0..<s1.count {
 8             dp[i &+ 1][0] = dp[i][0] &+ s1[i]
 9         }
10         for j in 0..<s2.count {
11             dp[0][j &+ 1] = dp[0][j] &+ s2[j]
12         }
13         for i in 1..<s1.count &+ 1 {
14             for j in 1..<s2.count &+ 1 {
15                 if s1[i - 1] == s2[j - 1] {
16                     dp[i][j] = dp[i - 1][j - 1]
17                 } else {
18                     dp[i][j] = min(s2[j - 1] &+ dp[i][j - 1], s1[i - 1] &+ dp[i - 1][j])
19                 }
20             }
21         }
22         
23         return dp[s1.count][s2.count]
24     }
25 }

---

436ms

 1 class Solution {
 2     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 3        var v = 97
 4         var map = [Character: Int]()
 5        "abcdefghijklmnopqrstuvwxyz".map { map[$0] = v; v += 1}
 6         let m = s1.count, n = s2.count
 7         let chars1 = Array(s1), chars2 = Array(s2)
 8         var dp = [[Int]](repeating: [Int](repeating: 0, count: n+1), count: m+1)
 9         for j in 1...n {
10             dp[0][j] = dp[0][j-1] + map[chars2[j-1]]!
11         }
12         for i in 1...m {
13             dp[i][0] = dp[i-1][0] + map[chars1[i-1]]!
14             for j in 1...n {
15                 if chars1[i-1] == chars2[j-1] {
16                     dp[i][j] = dp[i-1][j-1]
17                 }
18                 else {
19                     dp[i][j] = min(dp[i-1][j] + map[chars1[i-1]]!, dp[i][j-1] + map[chars2[j-1]]!)
20                 }
21             }
22         }
23         return dp[m][n]
24     }
25 }
26 
27 extension Character {
28     var ascii: Int {
29         return Int(unicodeScalars.first?.value ?? 0)
30     }
31 }

---

548ms

 1 class Solution {
 2     var map = [Character: Int]()
 3     var ans = Int.max
 4     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 5         var v = 97
 6        "abcdefghijklmnopqrstuvwxyz".map { map[$0] = v; v += 1}
 7         let m = s1.count, n = s2.count
 8         let chars1 = Array(s1), chars2 = Array(s2)
 9         var dp = [[Int]](repeating: [Int](repeating: 0, count: n+1), count: m+1)
10         for j in 1...n {
11             dp[0][j] = dp[0][j-1] + map[chars2[j-1]]!
12         }
13         for i in 1...m {
14             dp[i][0] = dp[i-1][0] + map[chars1[i-1]]!
15             for j in 1...n {
16                 if chars1[i-1] == chars2[j-1] {
17                     dp[i][j] = dp[i-1][j-1]
18                 }
19                 else {
20                     dp[i][j] = min(dp[i-1][j] + map[chars1[i-1]]!, dp[i][j-1] + map[chars2[j-1]]!)
21                 }
22             }
23         }
24         return dp[m][n]
25     }
26 
27     func dfs(_ s1: [Character], _ index1: Int, _ s2: [Character], _ index2: Int, _ sum: Int) {
28                 
29         if sum > ans {
30             return
31         }
32 
33         if index1 >= s1.count && index2 >= s2.count {
34             ans = min(ans, sum)
35             return
36         }
37 
38         if index1 < s1.count && index2 < s2.count {
39 
40             if s1[index1] == s2[index2] {
41                 dfs(s1, index1+1, s2, index2+1, sum)
42                 return
43             }
44             dfs(s1, index1+1, s2, index2, sum + map[s1[index1]]!)
45             dfs(s1, index1, s2, index2+1, sum + map[s2[index2]]!)
46             dfs(s1, index1+1, s2, index2+1, sum + map[s2[index2]]! + map[s1[index1]]!)
47         }
48         else if index1 >= s1.count && index2 < s2.count {            
49             dfs(s1, index1, s2, index2+1, sum + map[s2[index2]]!)
50         }
51         else if index1 < s1.count && index2 >= s2.count {
52             dfs(s1, index1+1, s2, index2, sum + map[s1[index1]]!)
53         }
54     }
55 }

---

604ms

 1 class Solution {
 2     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 3     var mem = [[Int?]](repeating: [Int?](repeating: nil, count: s2.count + 1), count: s1.count + 1)
 4     return minimumDeleteSumRecursion(Array(s1), Array(s2), 0, s2Index: 0, mem: &mem)
 5 }
 6 
 7 func minimumDeleteSumRecursion(_ s1 : [Character], _ s2 : [Character], _ s1Index : Int, s2Index : Int, mem : inout [[Int?]])->Int{
 8     
 9     guard s1Index < s1.count || s2Index < s2.count else{
10         return 0
11     }
12     
13     if let answer = mem[s1Index][s2Index]{
14         return answer
15     }
16     
17     if s1Index == s1.count{
18         mem[s1Index][s2Index] = Int(s2[s2Index].unicodeScalars.first!.value) + minimumDeleteSumRecursion(s1, s2, s1Index, s2Index: s2Index + 1, mem: &mem)
19         return mem[s1Index][s2Index]!
20     }else if s2Index == s2.count{
21         mem[s1Index][s2Index] = Int(s1[s1Index].unicodeScalars.first!.value) + minimumDeleteSumRecursion(s1, s2, s1Index + 1, s2Index: s2Index, mem: &mem)
22         return mem[s1Index][s2Index]!
23     }else{
24         if s1[s1Index] == s2[s2Index]{
25             mem[s1Index][s2Index] = minimumDeleteSumRecursion(s1, s2, s1Index + 1, s2Index: s2Index + 1, mem: &mem)
26             return mem[s1Index][s2Index]!
27         }else{
28             // we need to delete
29             let firstValue = Int(s1[s1Index].unicodeScalars.first!.value) + minimumDeleteSumRecursion(s1, s2, s1Index + 1, s2Index: s2Index, mem: &mem)
30             let secondValue = Int(s2[s2Index].unicodeScalars.first!.value) + minimumDeleteSumRecursion(s1, s2, s1Index, s2Index: s2Index + 1, mem: &mem)
31             mem[s1Index][s2Index] = min(firstValue, secondValue)
32             return mem[s1Index][s2Index]!
33         }
34     }
35   }
36 }

---

632ms

 1 class Solution {
 2     func minimumDeleteSum(_ s1: String, _ s2: String) -> Int {
 3     let s1 = Array(s1)
 4     let s2 = Array(s2)
 5     var matrix = [[Int]](repeating: [Int](repeating: 0, count: s2.count + 1), count: s1.count + 1)
 6     for s1Index in (0..<s1.count).reversed(){
 7         matrix[s1Index][s2.count] = matrix[s1Index + 1][s2.count] +  Int(s1[s1Index].unicodeScalars.first!.value)
 8     }
 9     for s2Index in (0..<s2.count).reversed(){
10         matrix[s1.count][s2Index] = matrix[s1.count][s2Index + 1] +  Int(s2[s2Index].unicodeScalars.first!.value)
11     }
12     for s1Index in (0..<s1.count).reversed(){
13         for s2Index in (0..<s2.count).reversed(){
14             if s1[s1Index] == s2[s2Index]{
15                 matrix[s1Index][s2Index] = matrix[s1Index + 1][s2Index + 1]
16             }else{
17                 let firstValue = Int(s1[s1Index].unicodeScalars.first!.value) + matrix[s1Index + 1][s2Index]
18                 let secondValue = Int(s2[s2Index].unicodeScalars.first!.value) + matrix[s1Index][s2Index + 1]
19                 matrix[s1Index][s2Index] = min(firstValue, secondValue)
20             }
21         }
22     }
23     return matrix[0][0]
24     }
25 }