Add Binary Tree Symmetry

Author: marttp

kotlin/Trees/BinaryTreeSymmetry.kt

@@ -0,0 +1,40 @@
+import ds.TreeNode
+
+/*
+    Definition of TreeNode:
+
+    data class TreeNode(
+        var value: Int,
+        var left: TreeNode? = null,
+        var right: TreeNode? = null
+    )
+*/
+
+fun binaryTreeSymmetry(root: TreeNode?): Boolean {
+    if (root == null) {
+        return true
+    }
+    return compareTrees(root.left, root.right)
+}
+
+fun compareTrees(node1: TreeNode?, node2: TreeNode?): Boolean {
+    // Base case: if both nodes are null, they're symmetric.
+    if (node1 == null && node2 == null) {
+        return true
+    }
+    // If one node is null and the other isn't, they aren't symmetric.
+    if (node1 == null || node2 == null) {
+        return false
+    }
+    // If the values of the current nodes don't match, trees aren't symmetric.
+    if (node1.value != node2.value) {
+        return false
+    }
+    // Compare the 'node1's left subtree with 'node2's right subtree. If these
+    // aren't symmetric, the whole tree is not symmetric.
+    if (!compareTrees(node1.left, node2.right)) {
+        return false
+    }
+    // Compare the 'node1's right subtree with 'node2's left subtree.
+    return compareTrees(node1.right, node2.left)
+}