graph Valid Tree solution

Author: doh6077

graph-valid-tree/doh6077.py

@@ -0,0 +1,33 @@
+class Solution:
+    def validTree(self, n: int, edges: List[List[int]]) -> bool:
+        # Valid Tree
+        # 1. no loop
+        # 2. no disconnected node 
+        # Use DFS and Hashset to track visited nodes 
+        if not n:
+            return True
+        
+        adj = {i:[] for i in range(n)}
+        for n1, n2 in edges:
+            adj[n1].append(n2)
+            adj[n2].append(n1)
+        visit = set()
+        def dfs(i, prev):
+            # Base case
+            if i in visit:
+                return False
+            visit.add(i)
+            # check neighbor nodes 
+            for j in adj[i]:
+                if j == prev:
+                    continue
+                if not dfs(j,i):
+                    return False
+            return True
+
+        return dfs(0, -1) and n == len(visit)
+
+
+
+        
+