no message

Author: partho-maple

leetcode.com/swift/DS_ALGO_PRAC.playground/Sources/swift/742_Closest_Leaf_in_a_Binary_Tree.swift

@@ -0,0 +1,40 @@
+import Foundation
+
+class Solution {
+    func findClosestLeaf(_ root: TreeNode?, _ k: Int) -> Int {
+        var graph = [Int:[Int]](), queue = [(TreeNode?, TreeNode)]() // (currentNode, parentNode)
+        queue.append((root, TreeNode(Int.max)))
+
+        // Creates the graph.
+        while !queue.isEmpty {
+            let (node, parentNode) = queue.removeFirst()
+            if let node = node {
+                graph[node.val, default: [Int]()].append(parentNode.val)
+                graph[parentNode.val, default: [Int]()].append(node.val)
+                queue.append((node.left, node))
+                queue.append((node.right, node))
+            }
+        }
+
+        var valQueue = [Int](), visited = Set<Int>()
+        valQueue.append(k)
+        while !valQueue.isEmpty {
+            let currentNodeVal = valQueue.removeFirst()
+            visited.insert(currentNodeVal)
+            if let neighbours = graph[currentNodeVal] {
+                if neighbours.count <= 1 && currentNodeVal != Int.max {
+                    return currentNodeVal
+                }
+                for i in 0..<neighbours.count {
+                    let neighbour = neighbours[i]
+                    if !visited.contains(neighbour) {
+                        valQueue.append(neighbour)
+                    }
+                }
+            } else {
+                return currentNodeVal
+            }
+        }
+        return -1
+    }
+}