lowest common ancestor of a binary search tree

Author: eunhwa99

lowest-common-ancestor-of-a-binary-search-tree/eunhwa99.kt

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+class TreeNode(var `val`: Int = 0) {
+    var left: TreeNode? = null
+    var right: TreeNode? = null
+}
+
+
+class Solution {
+
+    // TC: O(H) - H: height of BST
+    // SC: O(1) - while loop: X stack
+    fun lowestCommonAncestor(root: TreeNode?, p: TreeNode?, q: TreeNode?): TreeNode? {
+
+        if (root == null || p == null || q == null) return null
+    
+        // BST: left < parent < right
+        var current = root
+        while(current != null){ 
+            if(current.`val` < p.`val` && current.`val` < q.`val`){
+                current = current.right
+            }
+            else if(current.`val` > p.`val` && current.`val` > q.`val`){
+                current = current.left
+            }
+            else return current
+        }
+        
+        return null
+    }
+   
+}