add: 二叉树的最近公共祖先

src/tree/lowest-common-ancestor-of-a-binary-tree.js

@@ -0,0 +1,20 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val) {
+ *     this.val = val;
+ *     this.left = this.right = null;
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @param {TreeNode} p
+ * @param {TreeNode} q
+ * @return {TreeNode}
+ */
+export const lowestCommonAncestor = function (root, p, q) {
+  if (!root || root === p || root === q) return root
+  const left = lowestCommonAncestor(root.left, p, q)
+  const right = lowestCommonAncestor(root.right, p, q)
+  if ((left === p && right === q) || (left === q && right === p)) return root
+  return left || right
+}