diff --git a/merge-intervals/lhc0506.js b/merge-intervals/lhc0506.js
new file mode 100644
index 000000000..a7ede0834
--- /dev/null
+++ b/merge-intervals/lhc0506.js
@@ -0,0 +1,36 @@
+/**
+ * @param {number[][]} intervals
+ * @return {number[][]}
+ */
+var merge = function(intervals) {
+  const sortedIntervals = intervals.toSorted((a, b) => a[0] - b[0]);
+
+  if (intervals.length === 1) {
+      return intervals;
+  }
+
+  const result = [];
+  let [start, end] = sortedIntervals[0];
+
+
+  for (let i = 1; i < sortedIntervals.length; i++) {
+      const [currentStart, currentEnd] = sortedIntervals[i];
+
+      if (currentStart <= end) {
+          end = Math.max(end, currentEnd);
+      } else {
+          result.push([start, end]);
+          start = currentStart;
+          end = currentEnd;
+      }
+
+      if (i === sortedIntervals.length - 1) {
+          result.push([start, end]);
+      }
+  }
+
+  return result;
+};
+
+// 시간 복잡도: O(nlogn)
+// 공간 복잡도: O(n)
diff --git a/missing-number/lhc0506.js b/missing-number/lhc0506.js
new file mode 100644
index 000000000..77c3e32fc
--- /dev/null
+++ b/missing-number/lhc0506.js
@@ -0,0 +1,18 @@
+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var missingNumber = function(nums) {
+  const n = nums.length;
+  const array = new Array(n).fill(false);
+
+  for (let i = 0; i < n; i++) {
+      array[nums[i]] = true;
+  }
+
+  const index = array.findIndex(item => item === false);
+  return index === -1 ? n : index;
+};
+
+// 시간 복잡도: O(n)
+// 공간 복잡도: O(n)
diff --git a/reorder-list/lhc0506.js b/reorder-list/lhc0506.js
new file mode 100644
index 000000000..6abb1c71c
--- /dev/null
+++ b/reorder-list/lhc0506.js
@@ -0,0 +1,34 @@
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val, next) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.next = (next===undefined ? null : next)
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {void} Do not return anything, modify head in-place instead.
+ */
+var reorderList = function(head) {
+  const nodes = {};
+  let currentNode = head;
+  let i = 0;
+  while (currentNode) {
+      nodes[i] = currentNode;
+      currentNode = currentNode.next;
+      i++;
+  }
+
+  i--;
+
+  for (let j = 0; j < (i / 2); j++) {
+      nodes[j].next = nodes[i - j];
+      nodes[i - j].next = nodes[j + 1];
+      console.log(j)
+  }
+
+  nodes[Math.ceil(i / 2)].next = null;
+};
+
+// 시간 복잡도: O(n)
+// 공간 복잡도: O(n)