Create 1361-validate-binary-tree-nodes.kt

Author: a93a

kotlin/1361-validate-binary-tree-nodes.kt

@@ -0,0 +1,32 @@
+class Solution {
+    fun validateBinaryTreeNodes(n: Int, leftChild: IntArray, rightChild: IntArray): Boolean {
+        val hasParent = hashSetOf<Int>().apply {
+            for (n in (leftChild + rightChild)) {
+                if (n != -1)
+                    this.add(n)
+            }
+        }
+
+        if (hasParent.size == n) return false
+
+        var root = -1
+        for (i in 0 until n) {
+            if (i !in hasParent) {
+                root = i
+                break
+            }
+        }
+
+        val visit = hashSetOf<Int>()
+        fun dfs(i: Int): Boolean {
+            if (i == -1) return true
+            if (i in visit) return false  
+
+            visit.add(i)
+
+            return dfs(leftChild[i]) && dfs(rightChild[i])
+        }
+
+        return dfs(root) && visit.size == n
+    }
+}