[Python] Clean & Concise - Time O(n^2), Space O(1)
python\nclass Solution(object):\n    def insertionSortList(self, head):\n        dummyHead= ListNode(0)\n        \n        def insert(head):\n            prev =
```python\nclass Solution(object):\n    def insertionSortList(self, head):\n        dummyHead= ListNode(0)\n        \n        def insert(head):\n            prev = dummyHead\n            curr = dummyHead.next\n            while curr and curr.val <= head.val:\n                prev = curr\n                curr = curr.next\n                \n            prev.next = head\n            head.next = curr\n        \n        while head != None:\n            next = head.next\n            insert(head)\n            head = next\n            \n        return dummyHead.next\n```\n**Complexity:**\n- Time: `O(N^2)`\n- Space: `O(1)`
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