Create 261-Graph-Valid-Tree.py

neetcode-gh · web-flow · commit 940fe99bcfa6 · 2022-03-27T23:39:06.000-07:00
diff --git a/261-Graph-Valid-Tree.py b/261-Graph-Valid-Tree.py
@@ -0,0 +1,29 @@
+# Problem is free on Lintcode 
+class Solution:
+    """
+    @param n: An integer
+    @param edges: a list of undirected edges
+    @return: true if it's a valid tree, or false
+    """
+    def validTree(self, n, edges):
+        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):
+            if i in visit:
+                return False
+            
+            visit.add(i)
+            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)
