solve

Author: sonjh1217

graph-valid-tree/sonjh1217.swift

@@ -0,0 +1,36 @@
+import Foundation
+
+class Solution {
+    // O(n) time / O(n) space
+    func validTree(_ n: Int, _ edges: [[Int]]) -> Bool {
+        guard edges.count == n - 1 else {
+            return false
+        }
+        
+        var connectedNodes = Array(repeating: [Int](), count: n)
+                
+        for edge in edges {
+            connectedNodes[edge[0]].append(edge[1])
+            connectedNodes[edge[1]].append(edge[0])
+        }
+        
+        var isVisiteds = Array(repeating: false, count: n)
+        var head = 0
+        var queue = [0]
+        isVisiteds[0] = true
+        
+        while head < queue.count {
+            let currentNode = queue[head]
+            head += 1
+            
+            for node in connectedNodes[currentNode] {
+                guard !isVisiteds[node] else { continue }
+                
+                isVisiteds[node] = true
+                queue.append(node)
+            }
+        }
+        
+        return isVisiteds.allSatisfy { $0 }
+    }
+}