Create 261-Graph-Valid-Tree.java

java/261-Graph-Valid-Tree.java

@@ -0,0 +1,40 @@
+public class Solution {
+
+    private Map<Integer, List<Integer>> adjacencyList = new HashMap<>();
+
+    public boolean validTree(int n, int[][] edges) {
+        if (n == 0 || n == 1) return true;
+
+        if (edges.length == 0) return false;
+
+        for (var edge: edges) {
+            var node1 = edge[0];
+            var node2 = edge[1];
+            adjacencyList.putIfAbsent(node1, new ArrayList<>());
+            adjacencyList.putIfAbsent(node2, new ArrayList<>());
+            adjacencyList.get(node1).add(node2);
+            adjacencyList.get(node2).add(node1);
+        }
+
+        Set<Integer> visited = new HashSet<>();
+
+        return depthFirstSearch(0, -1, visited) && visited.size() == n;
+    }
+
+    private boolean depthFirstSearch(int node, int previous, Set<Integer> visited) {
+        if (visited.contains(node)) 
+            return false;
+
+        visited.add(node);
+
+        for (var neighbor: adjacencyList.get(node)) {
+            if (neighbor == previous) 
+                continue;
+
+            if (!depthFirstSearch(neighbor, node, visited))
+                return false;
+        }
+
+        return true;
+    }
+}