Graph Valid Tree

Author: TonyKim9401

graph-valid-tree/TonyKim9401.java

@@ -0,0 +1,37 @@
+// TC: O(n * m)
+// n = the length of edges, m = the length of each element list of edges
+// SC: O(n)
+// n = recursively visit everywhere
+public class Solution {
+    public boolean validTree(int n, int[][] edges) {
+        if (edges.length != n - 1) return false;
+
+        List<List<Integer>> graph = new ArrayList<>();
+        for (int i = 0; i < n; i++) {
+            graph.add(new ArrayList<>());
+        }
+
+        for (int[] edge : edges) {
+            graph.get(edge[0]).add(edge[1]);
+            graph.get(edge[1]).add(edge[0]);
+        }
+
+        boolean[] visited = new boolean[n];
+        if (!dfs(0, -1, graph, visited)) return false;
+
+        for (boolean v : visited) if(!v) return false;
+
+        return true;
+    }
+
+    private boolean dfs(int node, int parent, List<List<Integer>> graph, boolean[] visited) {
+        visited[node] = true;
+
+        for (int neighbor : graph.get(node)) {
+            if (neighbor == parent) continue;
+            if (visited[neighbor]) return false;
+            if (!dfs(neighbor, node, graph, visited)) return false;
+        }
+        return true;
+    }
+}