777_Swap_Adjacent_in_LR_String

Author: partho-maple

README.md

@@ -836,6 +836,7 @@ BFS, DFS, Dijkstra, Floyd–Warshall, Bellman-Ford, Kruskal, Prim's, Minimum Spa
 |13| **[319. Bulb Switcher](https://tinyurl.com/ycygg2ju)** | [Python](https://tinyurl.com/wu6rdaw/319_Bulb_Switcher.py)| [Art 1](https://tinyurl.com/y886rzfe), [Art 2](https://tinyurl.com/y9n7vo2x), [Art 3](https://tinyurl.com/ya3fookw) | Medium (Really!!??) | Are you fucking kidding me!! We are programmers, not math wizard. |
 |14| **[1344. Angle Between Hands of a Clock](https://tinyurl.com/yy3g8mg6)** | [Python](https://tinyurl.com/wu6rdaw/1344_Angle_Between_Hands_of_a_Clock.py), [Swift](https://tinyurl.com/wuja3c4/1344_Angle_Between_Hands_of_a_Clock.swift)| --- | Medium | FB really likes to ask tricky question. |
 |15| **[1276. Number of Burgers with No Waste of Ingredients](https://tinyurl.com/y4dl7mne)** | [Python](https://tinyurl.com/wu6rdaw/1276_Number_of_Burgers_with_No_Waste_of_Ingredients.py), [Swift](https://tinyurl.com/wuja3c4/1276_Number_of_Burgers_with_No_Waste_of_Ingredients.swift)| [Art 1](https://tinyurl.com/y2u668aa), [Art 2](https://tinyurl.com/y2u9nvre), [Art 3](https://tinyurl.com/yxdzbp9s) | Medium | Pure math |
+|16| **[777. Swap Adjacent in LR String](https://tinyurl.com/y2syu722)** | [Python](https://tinyurl.com/wu6rdaw/777_Swap_Adjacent_in_LR_String.py), [Swift](https://tinyurl.com/wuja3c4/777_Swap_Adjacent_in_LR_String.swift)| [Art 1](https://tinyurl.com/y6cfe8gy) | Medium | Brainteser |
 
 </p>
 </details>

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/777_Swap_Adjacent_in_LR_String.swift

@@ -0,0 +1,79 @@
+import Foundation
+
+// My solution during MOC. Wrong answer
+class Solution {
+    func canTransform(_ start: String, _ end: String) -> Bool {
+        var start = Array(start)
+        var end = Array(end)
+        guard start.count == end.count else {
+            return false
+        }
+        
+        var start_ptr = 0
+        while start_ptr < start.count {
+            if start[start_ptr] != end[start_ptr] {
+                if start_ptr + 1 < start.count && ((start[start_ptr] == "X" && start[start_ptr + 1] == "L") || (start[start_ptr] == "R" && start[start_ptr + 1] == "X")) {
+                    start.swapAt(start_ptr, start_ptr + 1)
+                    if start[start_ptr] == end[start_ptr] && start[start_ptr + 1] == end[start_ptr + 1] {
+                        start_ptr += 1
+                    } else {
+                        return false
+                    }
+                } else {
+                    return false
+                }
+            }
+            start_ptr += 1
+        }
+        return true
+    }
+}
+
+// Source: https://tinyurl.com/y6cfe8gy
+// Accepted
+class Solution {
+    func canTransform(_ start: String, _ end: String) -> Bool {
+        var startArray = Array(start)
+        var endArray = Array(end)
+        
+        guard startArray.count == endArray.count else {
+            return false
+        }
+        
+        if start.replacingOccurrences(of: "X", with: "") != end.replacingOccurrences(of: "X", with: "") {
+            return false
+        }
+        
+        var (L_start, L_end) = ([Int](), [Int]())
+        var (R_start, R_end) = ([Int](), [Int]())
+        
+        for i in 0..<startArray.count {
+            if startArray[i] == "L" {
+                L_start.append(i)
+            }
+            if endArray[i] == "L" {
+                L_end.append(i)
+            }
+            
+            if startArray[i] == "R" {
+                R_start.append(i)
+            }
+            if endArray[i] == "R" {
+                R_end.append(i)
+            }
+        }
+        
+        for (i, j) in zip(L_start, L_end) {
+            if i < j {
+                return false
+            }
+        }
+        
+        for (i, j) in zip(R_start, R_end) {
+            if i > j {
+                return false
+            }
+        }
+        return true
+    }
+}