Create 0652-find-duplicate-subtrees.kt

a93a · web-flow · commit 6e3731f68ceb · 2023-02-28T12:28:43.000+01:00
diff --git a/kotlin/0652-find-duplicate-subtrees.kt b/kotlin/0652-find-duplicate-subtrees.kt
@@ -0,0 +1,33 @@
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun findDuplicateSubtrees(root: TreeNode?): List<TreeNode?> {
+        val res = ArrayList<TreeNode?>()
+        val subTrees = HashMap<String, Int>()
+
+        fun preOrder(root: TreeNode?): String {
+            root?: return "null"
+            val s = ",${root.value},${preOrder(root.left)},${preOrder(root.right)}"
+            if(subTrees.contains(s)){
+                if(subTrees[s] == 1) {
+                    res.add(root)
+                }
+            }
+            subTrees[s] = subTrees.getOrDefault(s, 0) + 1       
+            return s
+        }
+
+        preOrder(root)
+        return res
+    }
+
+    val TreeNode.value get() = this.`val`
+}
