solves lowest cmmon ancestor

Author: anishLearnsToCode

README.md

@@ -3,8 +3,8 @@
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src/LowestCommonAncestorOfBinarySearchTree.java

@@ -0,0 +1,36 @@
+import java.util.ArrayList;
+import java.util.List;
+
+public class LowestCommonAncestorOfBinarySearchTree {
+    private static class TreeNode {
+        int val;
+        TreeNode left;
+        TreeNode right;
+    }
+
+    public TreeNode lowestCommonAncestor(TreeNode root, TreeNode p, TreeNode q) {
+        List<TreeNode> pathToP = pathTo(root, p);
+        List<TreeNode> pathToQ = pathTo(root, q);
+        return lowestCommonAncestor(pathToP, pathToQ);
+    }
+
+    private static List<TreeNode> pathTo(TreeNode root, TreeNode to) {
+        List<TreeNode> path = new ArrayList<>();
+        while (root != to) {
+            path.add(root);
+            if (to.val < root.val) root = root.left;
+            else root = root.right;
+        }
+        path.add(to);
+        return path;
+    }
+
+    private static TreeNode lowestCommonAncestor(List<TreeNode> path1, List<TreeNode> path2) {
+        for (int index = 1 ; index < Math.min(path1.size(), path2.size()) ; index++) {
+            if (!path1.get(index).equals(path2.get(index))) {
+                return path1.get(index - 1);
+            }
+        }
+        return path1.get(Math.min(path1.size(), path2.size()) - 1);
+    }
+}