Added Solution Merge K Sorted List

Leetcode Practice/merge_k_sorted_list.py

@@ -0,0 +1,86 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    # def mergeKLists(self, lists):
+    #     # Priority queue
+    #     from Queue import PriorityQueue
+    #     queue = PriorityQueue()
+    #     for l in lists:
+    #         while l is not None:
+    #             queue.put((l.val, l))
+    #             l = l.next
+    #     p = dummyHead = ListNode(-1)
+    #     while queue.qsize() > 0:
+    #         p.next = queue.get()[1]
+    #         p = p.next
+    #     p.next = None
+    #     return dummyHead.next
+
+
+    # def mergeKLists(self, lists):
+    #     """
+    #     :type lists: List[ListNode]
+    #     :rtype: ListNode
+    #     """
+    #     # sort
+    #     v_map = {}
+    #     # hash
+    #     for l in lists:
+    #         while l is not None:
+    #             try:
+    #                 v_map[l.val].append(l)
+    #             except KeyError:
+    #                 v_map[l.val] = [l]
+    #             l = l.next
+    #     head = last = ListNode(-1)
+    #     # sort and connect
+    #     for k in sorted(v_map.keys()):
+    #         for t in v_map[k]:
+    #             last.next = t
+    #             last = t
+    #     last.next = None
+    #     return head.next
+
+
+
+
+    def mergeKLists(self, lists):
+        # recursive
+        if lists is None:
+            return None
+        elif len(lists) == 0:
+            return None
+        return self.mergeK(lists, 0, len(lists) - 1)
+
+    def mergeK(self, lists, low, high):
+        if low == high:
+            return lists[low]
+        elif low + 1 == high:
+            return self.mergeTwolists(lists[low], lists[high])
+        mid = (low + high) / 2
+        return self.mergeTwolists(self.mergeK(lists, low, mid), self.mergeK(lists, mid + 1, high))
+
+    def mergeTwolists(self, l1, l2):
+        if l1 is None:
+            return l2
+        if l2 is None:
+            return l1
+        head = curr = ListNode(-1)
+        while l1 is not None and l2 is not None:
+            if l1.val <= l2.val:
+                curr.next = l1
+                l1 = l1.next
+            else:
+                curr.next = l2
+                l2 = l2.next
+            curr = curr.next
+        if l1 is not None:
+            curr.next = l1
+        if l2 is not None:
+            curr.next = l2
+        return head.next
+