Given a string S, we can transform every letter individually to be lowercase or uppercase to create another string. Return a list of all possible strings we could create.
Examples: Input: S = "a1b2" Output: ["a1b2", "a1B2", "A1b2", "A1B2"] Input: S = "3z4" Output: ["3z4", "3Z4"] Input: S = "12345" Output: ["12345"]
Note:
-
Swill be a string with length between1and12. -
Swill consist only of letters or digits.
给定一个字符串S，通过将字符串S中的每个字母转变大小写，我们可以获得一个新的字符串。返回所有可能得到的字符串集合。
示例: 输入: S = "a1b2" 输出: ["a1b2", "a1B2", "A1b2", "A1B2"] 输入: S = "3z4" 输出: ["3z4", "3Z4"] 输入: S = "12345" 输出: ["12345"]
注意：
-
S的长度不超过12。 -
S仅由数字和字母组成。
96ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 let arr = Array(S.uppercased().cString(using: .ascii)!)
4 var ans = [String]()
5 ans.reserveCapacity(1024)
6
7 var tmp = [CChar](repeating: 0, count: arr.count + 1)
8
9 func step(_ tmp: inout [CChar], _ idx: Int) {
10 if idx == arr.count - 1 {
11 ans.append(String(cString: tmp))
12 } else if arr[idx] < 65 {
13 tmp[idx] = arr[idx]
14 step(&tmp, idx + 1)
15 } else {
16 tmp[idx] = arr[idx]
17 step(&tmp, idx + 1)
18 tmp[idx] = arr[idx] + 32
19 step(&tmp, idx + 1)
20 }
21 }
22
23 step(&tmp, 0)
24 return ans
25 }
26 }
112ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var list: [String] = []
4 if S.isEmpty {
5 return [S]
6 }
7
8 if let _ = Int(S) {
9 return [S]
10 }
11 var source = S
12 for _ in 0..<source.count {
13 let c = source.removeFirst()
14 letterCaseRec(c: c, list: &list)
15 }
16 return list
17 }
18
19
20 func letterCaseRec(c: Character, list: inout [String]) {
21
22 var opp:String? = nil
23 if list.isEmpty {
24 list.append(String(c))
25 if let _ = Int(String(c)) {
26 } else {
27 opp = String(c) == String(c).capitalized ? String(c).lowercased() : String(c).capitalized
28 list.append(opp!)
29 }
30 return
31 }
32
33 if let _ = Int(String(c)) {
34 for x in 0..<list.count {
35 list[x].append(c)
36 }
37 } else {
38 opp = String(c) == String(c).capitalized ? String(c).lowercased() : String(c).capitalized
39 let size = list.count
40 for x in 0..<size {
41 let current = list[x]
42 list.append(current + opp!)
43 list[x].append(c)
44 }
45 }
46 }
47 }
116ms
1 class Solution {
2
3 func letterCasePermutation(_ S: String) -> [String] {
4 var result = [String]()
5 letterCasePermutation(S, 0, "", &result)
6 return result
7 }
8
9 func letterCasePermutation(_ S: String, _ index: Int, _ currentS: String, _ result: inout [String]) {
10 if index >= S.count {
11 result.append(currentS)
12 return
13 }
14
15 let char = S[S.index(S.startIndex, offsetBy: index)]
16 letterCasePermutation(S, index+1, (currentS+String(char).lowercased()), &result)
17 if let c = char.unicodeScalars.first, CharacterSet.letters.contains(c) {
18 letterCasePermutation(S, index+1, (currentS+String(char).uppercased()), &result)
19 }
20 }
21 }
124ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var cur = String(), res = [String]()
4 var sChars = Array(S)
5 recursion(&sChars, 0, &res)
6 return res
7 }
8
9 private func recursion(_ sChars: inout [Character], _ i: Int, _ res: inout [String]) {
10 if i == sChars.count {
11 res.append(String(sChars))
12 return
13 }
14
15 recursion(&sChars, i + 1, &res)
16
17 if sChars[i] >= "0" && sChars[i] <= "9" { return } // it a number
18 sChars[i] = toggleCase(sChars[i])
19 recursion(&sChars, i + 1, &res)
20 sChars[i] = toggleCase(sChars[i])
21
22 }
23
24 private func toggleCase(_ char: Character) -> Character {
25 let s = String(char)
26 if s.uppercased() == s {
27 return Character(s.lowercased())
28 } else {
29 return Character(s.uppercased())
30 }
31 }
32 }
128ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var result = [String]()
4 result.append(S.lowercased())
5 if Int(S) != nil {
6 return result
7 }
8 for (k,i) in S.enumerated() {
9 if(Int(String(i)) != nil) {
10 continue
11 }
12 for j in 0..<result.count {
13 var entry = Array(result[j])
14 entry[k] = Character(String(entry[k]).uppercased())
15 result.append(String(entry))
16 }
17
18 }
19 return result
20 }
21 }
132ms
1 class Solution {
2 func patternToString(_ pattern: String, _ source: String) -> String {
3 var result = ""
4 var posInPattern = 0
5 let upperSource = source.uppercased()
6 for i in 0..<source.count {
7 let s = source[source.index(source.startIndex, offsetBy: i)]
8 if s >= "a" && s <= "z" {
9 let S = upperSource[upperSource.index(upperSource.startIndex, offsetBy: i)]
10 result.append(pattern[pattern.index(pattern.startIndex, offsetBy: posInPattern)] == "0" ? s : S)
11 posInPattern += 1
12 } else {
13 result.append(s)
14 }
15 }
16 return result
17 }
18
19 func letterCasePermutation(_ S: String) -> [String] {
20 let s = S.lowercased()
21 var count = 1
22 var bitCount = 0
23 for c in s {
24 if c >= "a" && c <= "z" {
25 count *= 2
26 bitCount += 1
27 }
28 }
29
30 guard bitCount > 0 else {
31 return [S]
32 }
33
34 var result = [String]()
35 for i in 0..<count {
36 var binStr = String(i, radix: 2)
37 if binStr.count < bitCount {
38 binStr = String(repeating: "0", count: bitCount - binStr.count) + binStr
39 }
40 result.append(patternToString(binStr, s))
41 }
42 return result
43 }
44 }
140ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var result = [String]()
4 dfs(S, 0, "", &result, S.count)
5 return result
6 }
7
8 func dfs(_ S: String,
9 _ index: Int,
10 _ currentS: String,
11 _ result: inout [String],
12 _ lengthS: Int) {
13 if index >= lengthS {
14 result.append(currentS)
15 return
16 }
17
18 let char = S[S.index(S.startIndex, offsetBy: index)]
19 dfs(S,
20 index+1,
21 (currentS+String(char).lowercased()),
22 &result,
23 lengthS)
24 if let c = char.unicodeScalars.first, CharacterSet.letters.contains(c) {
25 dfs(S,
26 index+1,
27 (currentS+String(char).uppercased()),
28 &result,
29 lengthS)
30 }
31 }
32 }
180ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var res: [[String]] = [[]]
4
5 for char in S {
6 if isAlpha(char) {
7 for i in 0..<res.count {
8 res.append(res[i])
9 res[i].append(String(char).lowercased())
10 res[res.count-1].append(String(char).uppercased())
11 }
12 } else {
13 for (i, var s) in res.enumerated() {
14 s.append(String(char))
15 res[i] = s
16 }
17 }
18 }
19
20 return res.map { $0.joined() }
21 }
22
23 private func isAlpha(_ char: Character) -> Bool {
24 if let value = char.unicodeScalars.first?.value {
25 if (value > 64 && value < 91) || (value > 96 && value < 123) {
26 return true;
27 }
28 }
29 return false;
30 }
31 }
Runtime: 196 ms Memory Usage: 20.5 MB
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3 var S = S
4 var res:[String] = [String]()
5 helper(&S, 0, &res)
6 return res
7 }
8
9 func helper(_ s:inout String,_ pos:Int,_ res:inout [String])
10 {
11 var arrChar:[Character] = Array(s)
12 var arrInt:[Int] = arrChar.map{$0.ascii}
13 if pos == s.count
14 {
15 res.append(s)
16 return
17 }
18 helper(&s, pos + 1, &res)
19 if arrInt[pos] > 57
20 {
21 arrInt[pos] ^= 32;
22 arrChar = arrInt.map{$0.ASCII}
23 s = String(arrChar)
24 helper(&s, pos + 1, &res);
25 }
26 }
27 }
28
29 //String扩展
30 extension String {
31 //subscript函数可以检索数组中的值
32 //直接按照索引方式截取指定索引的字符
33 subscript (_ i: Int) -> Character {
34 //读取字符
35 get {return self[index(startIndex, offsetBy: i)]}
36 }
37 }
38
39 //Character扩展
40 extension Character
41 {
42 //Character转ASCII整数值(定义小写为整数值)
43 var ascii: Int {
44 get {
45 return Int(self.unicodeScalars.first?.value ?? 0)
46 }
47 }
48 }
49
50 //Int扩展
51 extension Int
52 {
53 //Int转Character,ASCII值(定义大写为字符值)
54 var ASCII:Character
55 {
56 get {return Character(UnicodeScalar(self)!)}
57 }
58 }
232ms
1 class Solution {
2 var res = [String]()
3 func letterCasePermutation(_ S: String) -> [String] {
4 var wordsArr = [String]()
5 for c in S{
6 wordsArr.append(String(c))
7 }
8 dps("",wordsArr)
9 return res
10 }
11
12 func dps(_ head:String, _ foot:[String]) -> Void{
13 if foot.count == 0{
14 res.append(head)
15 return
16 }
17 var s:String = foot.first!
18 var newfoot = foot
19 newfoot.removeFirst()
20 if s <= "9" {
21 dps(head+s,newfoot)
22 }else{
23 dps(head+String(s.lowercased()),newfoot)
24 dps(head+String(s.uppercased()),newfoot)
25 }
26 }
27 }
256ms
1 class Solution {
2 func letterCasePermutation(_ S: String) -> [String] {
3
4 func isNum( _ s : String) -> Bool {
5 let scan = Scanner(string: s)
6 var val : Int = 0
7 return scan.scanInt(&val) && scan.isAtEnd
8 }
9
10 func char(at i : Int, _ s : String) -> String {
11 return String(s[s.index(s.startIndex, offsetBy: i)])
12 }
13
14 var source : [String] = []
15 for i in 0 ..< S.count {
16 source.append(char(at: i, S))
17 }
18 var res = [String]()
19 let n = S.count
20 func backTrace(t : Int, src : [String], s : String) {
21 if t >= n {
22 res.append(s)
23 } else {
24 if isNum(source[t]) {
25 backTrace(t: t+1, src: source, s: s+source[t])
26 return
27 }
28 for i in 0 ... 1 {
29 if i == 0 { //小写
30 backTrace(t: t+1, src: source, s: s+source[t].lowercased())
31
32 } else { // i == 1 大写
33 backTrace(t: t+1, src: source, s: s+source[t].uppercased())
34 }
35 }
36 }
37 }
38 backTrace(t: 0, src: source, s: "")
39 return res
40 }
41 }