feat: Lowest Common Ancestor of a Binary Search Tree

Author: gwbaik9717

lowest-common-ancestor-of-a-binary-search-tree/gwbaik9717.js

@@ -0,0 +1,56 @@
+// Time complexity: O(logn)
+// Space complexity: O(logn)
+
+/**
+ * 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}
+ */
+var lowestCommonAncestor = function (root, p, q) {
+  // 1. 각자 부모 리스트 완성
+  const search = (target, parent) => {
+    const dfs = (current) => {
+      if (target.val > current.val) {
+        dfs(current.right);
+      }
+
+      if (target.val < current.val) {
+        dfs(current.left);
+      }
+
+      parent.push(current);
+    };
+
+    dfs(root);
+  };
+
+  const parentP = [];
+  const parentQ = [];
+
+  search(p, parentP);
+  search(q, parentQ);
+
+  // 2. 공통 부모 탐색
+  let answer = null;
+
+  while (
+    parentP.at(-1) &&
+    parentQ.at(-1) &&
+    parentP.at(-1).val === parentQ.at(-1).val
+  ) {
+    answer = parentP.at(-1);
+    parentP.pop();
+    parentQ.pop();
+  }
+
+  return answer;
+};