solve : graph valid tree

Author: SamTheKorean

graph-valid-tree/samthekorean.py

@@ -0,0 +1,25 @@
+# O(n+e) where n is number of nodes and e is the number of edges.
+# O(n+e) where n is number of nodes and e is the number of edges.
+class Solution:
+    def validTree(self, numNodes: int, connections: List[List[int]]) -> bool:
+        adjacencyList = [[] for _ in range(numNodes)]
+        for src, dst in connections:
+            adjacencyList[src].append(dst)
+            adjacencyList[dst].append(src)
+
+        visitedNodes = set()
+
+        def detectCycle(currentNode, previousNode):
+            if currentNode in visitedNodes:
+                return True
+            visitedNodes.add(currentNode)
+            for neighbor in adjacencyList[currentNode]:
+                if neighbor == previousNode:
+                    continue
+                if detectCycle(neighbor, currentNode):
+                    return True
+            return False
+
+        if detectCycle(0, -1):
+            return False
+        return len(visitedNodes) == numNodes