Add Invert Binary Tree

Author: marttp

kotlin/Trees/InvertBinaryTreeIteretive.kt

@@ -0,0 +1,33 @@
+import java.util.Stack
+import ds.TreeNode
+
+/*
+    Definition of TreeNode:
+
+    data class TreeNode(
+        var value: Int, 
+        var left: TreeNode? = null, 
+        var right: TreeNode? = null
+    )
+*/
+
+fun invertBinaryTreeIterative(root: TreeNode?): TreeNode? {
+    if (root == null) return null
+    val stack = Stack<TreeNode>()
+    stack.push(root)
+    while (stack.isNotEmpty()) {
+        val node = stack.pop()
+        // Swap the left and right subtrees of the current node.
+        val temp = node.left
+        node.left = node.right
+        node.right = temp
+        // Push the left and right subtrees onto the stack.
+        if (node.left != null) {
+            stack.push(node.left)
+        }
+        if (node.right != null) {
+            stack.push(node.right)
+        }
+    }
+    return root
+}

kotlin/Trees/InvertBinaryTreeRecursive.kt

@@ -0,0 +1,26 @@
+import ds.TreeNode
+
+/*
+    Definition of TreeNode:
+
+    data class TreeNode(
+        var value: Int, 
+        var left: TreeNode? = null, 
+        var right: TreeNode? = null
+    )
+*/
+
+fun invertBinaryTreeRecursive(root: TreeNode?): TreeNode? {
+    // Base case: If the node is null, there's nothing to invert.
+    if (root == null) {
+        return null
+    }
+    // Swap the left and right subtrees of the current node.
+    val temp = root.left
+    root.left = root.right
+    root.right = temp
+    // Recursively invert the left and right subtrees.
+    invertBinaryTreeRecursive(root.left)
+    invertBinaryTreeRecursive(root.right)
+    return root
+}