LCA implementation (fixes #89)

src/_Problems_/lowest-common-ancestor-in-binary-search-tree/index.js

@@ -0,0 +1,24 @@
+/**
+ * Lowest Common Ancestor in a Binary Search Tree.
+ *
+ * Given values of two values n1 and n2 in a Binary Search Tree, find the Lowest Common Ancestor (LCA). You may assume that both the values exist in the tree.
+ */
+
+function lca(node, n1, n2) {
+  if (node == null)
+    return null;
+
+  // If both n1 and n2 are smaller than root, then LCA lies in left
+  if (node.data > n1 && node.data > n2)
+    return lca(node.left, n1, n2);
+
+  // If both n1 and n2 are greater than root, then LCA lies in right
+  if (node.data < n1 && node.data < n2)
+    return lca(node.right, n1, n2);
+
+  return node;
+}
+
+module.exports = {
+  lca,
+};

src/_Problems_/lowest-common-ancestor-in-binary-search-tree/index.test.js

@@ -0,0 +1,13 @@
+const { lca } = require('.');
+
+describe('LCA', () => {
+  it('Should return 12', () => {
+    expect(
+      lca(
+        {"left":{"left":{"data":4},"right":{"left":{"data":10},"right":{"data":14},"data":12},"data":8},"right":{"data":22},"data":20}
+        , 10
+        , 14)
+      .data).toEqual(12);
+  });
+});
+