[Swift]LeetCode777. 在LR字符串中交换相邻字符 | Swap Adjacent in LR String
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
➤微信公众号：山青咏芝（shanqingyongzhi）
➤博客园地址：山青咏芝（https://www.cnblogs.com/strengthen/）
➤GitHub地址：https://github.com/strengthen/LeetCode
➤原文地址： https://www.cnblogs.com/strengthen/p/10541711.html
➤如果链接不是山青咏芝的博客园地址，则可能是爬取作者的文章。
➤原文已修改更新！强烈建议点击原文地址阅读！支持作者！支持原创！
★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★★
In a string composed of 'L', 'R', and 'X'characters, like "RXXLRXRXL", a move consists of either replacing one occurrence of "XL" with "LX", or replacing one occurrence of "RX" with "XR". Given the starting string start and the ending string end, return True if and only if there exists a sequence of moves to transform one string to the other.
Example:
Input: start = "RXXLRXRXL", end = "XRLXXRRLX" Output: True Explanation: We can transform start to end following these steps: RXXLRXRXL -> XRXLRXRXL -> XRLXRXRXL -> XRLXXRRXL -> XRLXXRRLX
Note:
1 <= len(start) = len(end) <= 10000.- Both start and end will only consist of characters in
{'L', 'R', 'X'}.
在一个由 'L' , 'R' 和 'X' 三个字符组成的字符串（例如"RXXLRXRXL"）中进行移动操作。一次移动操作指用一个"LX"替换一个"XL"，或者用一个"XR"替换一个"RX"。现给定起始字符串start和结束字符串end，请编写代码，当且仅当存在一系列移动操作使得start可以转换成end时， 返回True。
示例 :
输入: start = "RXXLRXRXL", end = "XRLXXRRLX" 输出: True 解释: 我们可以通过以下几步将start转换成end: RXXLRXRXL -> XRXLRXRXL -> XRLXRXRXL -> XRLXXRRXL -> XRLXXRRLX
注意:
1 <= len(start) = len(end) <= 10000。start和end中的字符串仅限于'L','R'和'X'。
Runtime: 24 ms
Memory Usage: 19.5 MB
1 class Solution { 2 func canTransform(_ start: String, _ end: String) -> Bool { 3 var start = Array(start) 4 var end = Array(end) 5 var n:Int = start.count 6 var cntL:Int = 0 7 var cntR:Int = 0 8 for i in 0..<n 9 { 10 if start[i] == "R" {cntR += 1} 11 if end[i] == "L" {cntL += 1} 12 if start[i] == "L" {cntL -= 1} 13 if end[i] == "R" {cntR -= 1} 14 if cntL < 0 || cntR < 0 || cntL * cntR != 0 15 { 16 return false 17 } 18 } 19 return cntL == 0 && cntR == 0 20 } 21 }
68ms
1 class Solution { 2 func canTransform(_ start: String, _ end: String) -> Bool { 3 let cs = Array(start) 4 let ce = Array(end) 5 let ts = String(cs.filter{ $0 != "X" } ) 6 let te = String(ce.filter{ $0 != "X" } ) 7 8 guard ts == te else { return false } 9 10 var sr = [Int]() 11 var sl = [Int]() 12 13 for (i, char) in cs.enumerated() { 14 if char == "R" { 15 sr.append(i) 16 } else if char == "L" { 17 sl.append(i) 18 } 19 } 20 21 var rCount = 0 22 var lCount = 0 23 24 for (i, char) in ce.enumerated() { 25 if char == "R" { 26 if sr[rCount] > i { 27 return false 28 } else { 29 rCount += 1 30 } 31 } else if char == "L" { 32 if sl[lCount] < i { 33 return false 34 } else { 35 lCount += 1 36 } 37 } 38 } 39 40 return true 41 } 42 }
96ms
1 class Solution { 2 func compare(_ start: String, _ end: String) -> Bool { 3 var rs1 = 0 4 var ls1 = 0 5 var xs1 = 0 6 var rs2 = 0 7 var ls2 = 0 8 var xs2 = 0 9 for i in start.indices { 10 switch start[i] { 11 case "R": 12 rs1 += 1 13 case "L": 14 ls1 += 1 15 case "X": 16 xs1 += 1 17 default: 18 break 19 } 20 switch end[i] { 21 case "R": 22 rs2 += 1 23 case "L": 24 ls2 += 1 25 case "X": 26 xs2 += 1 27 default: 28 break 29 } 30 } 31 return rs1 == rs2 && ls1 == ls2 && xs1 == xs2 32 } 33 34 func canTransform(_ start: String, _ end: String) -> Bool { 35 var rs = [String.Index]() 36 var ls = [String.Index]() 37 for (i, ch) in zip(start.indices, start) { 38 if ch == "R" { 39 rs.append(i) 40 } else if ch == "L" { 41 ls.append(i) 42 } 43 } 44 rs.reverse() 45 ls.reverse() 46 47 if !compare(start, end) { 48 return false 49 } 50 51 for (i, ch) in zip(end.indices, end) { 52 if ch == "R" { 53 if let nextRIdx = rs.last, nextRIdx <= i { 54 if let nextLIdx = ls.last { 55 if nextLIdx < nextRIdx { 56 // impossible to move R through L 57 return false 58 } else { 59 rs.removeLast() 60 } 61 } else { 62 rs.removeLast() 63 } 64 } else { 65 return false 66 } 67 } else if ch == "L" { 68 if let nextLIdx = ls.last, nextLIdx >= i { 69 if let nextRIdx = rs.last { 70 if nextRIdx < nextLIdx { 71 // impossible to move L through R 72 return false 73 } else { 74 ls.removeLast() 75 } 76 } else { 77 ls.removeLast() 78 } 79 } else { 80 return false 81 } 82 } 83 } 84 return true 85 } 86 }
104ms
1 class Solution { 2 func canTransform(_ start: String, _ end: String) -> Bool { 3 guard start.count >= 1 && start.count <= 10000 && end.count >= 1 && end.count <= 10000 else { 4 return false 5 } 6 let startChars = Array(start), endChars = Array(end) 7 var startInfos = [(Character, Int)](), endInfos = [(Character, Int)]() 8 for (index, char) in startChars.enumerated() { 9 if char == "L" || char == "R" { 10 startInfos.append((char, index)) 11 } else if char != "X" { 12 return false 13 } 14 } 15 for (index, char) in endChars.enumerated() { 16 if char == "L" || char == "R" { 17 endInfos.append((char, index)) 18 } else if char != "X" { 19 return false 20 } 21 } 22 let startInfosChars = startInfos.map { 23 $0.0 24 } 25 let endInfosChars = endInfos.map { 26 $0.0 27 } 28 guard startInfosChars == endInfosChars else { 29 return false 30 } 31 for (index, startInfo) in startInfos.enumerated() { 32 let endInfo = endInfos[index] 33 if startInfo.0 == "L" { 34 guard startInfo.1 >= endInfo.1 else { 35 return false 36 } 37 } else { 38 guard startInfo.1 <= endInfo.1 else { 39 return false 40 } 41 } 42 } 43 return true 44 } 45 }
