diff --git a/merge-intervals/hu6r1s.py b/merge-intervals/hu6r1s.py
new file mode 100644
index 000000000..4478ac2a6
--- /dev/null
+++ b/merge-intervals/hu6r1s.py
@@ -0,0 +1,9 @@
+class Solution:
+    def merge(self, intervals: List[List[int]]) -> List[List[int]]:
+        result = []
+        for interval in sorted(intervals):
+            if not result or result[-1][1] < interval[0]:
+                result.append(interval)
+            else:
+                result[-1][1] = max(result[-1][1], interval[1])
+        return result
diff --git a/missing-number/hu6r1s.py b/missing-number/hu6r1s.py
new file mode 100644
index 000000000..d4d24af1c
--- /dev/null
+++ b/missing-number/hu6r1s.py
@@ -0,0 +1,6 @@
+class Solution:
+    def missingNumber(self, nums: List[int]) -> int:
+        for i in range(len(nums)):
+            if i not in nums:
+                return i
+        return len(nums)
diff --git a/reorder-list/hu6r1s.py b/reorder-list/hu6r1s.py
new file mode 100644
index 000000000..559f69259
--- /dev/null
+++ b/reorder-list/hu6r1s.py
@@ -0,0 +1,26 @@
+# Definition for singly-linked list.
+# class ListNode:
+#     def __init__(self, val=0, next=None):
+#         self.val = val
+#         self.next = next
+class Solution:
+    def reorderList(self, head: Optional[ListNode]) -> None:
+        """
+        Do not return anything, modify head in-place instead.
+        """
+        stack = []
+        node = head
+        while node:
+            stack.append(node)
+            node = node.next
+
+        node = dummy = ListNode(-1)
+        for i in range(len(stack)):
+            if i % 2:
+                node.next = stack.pop()
+            else:
+                node.next = head
+                head = head.next
+            node = node.next
+        node.next = None
+        return dummy.next