Create merge_sort_linked_list.py

排序算法/归并排序/merge_sort_linked_list.py

@@ -0,0 +1,75 @@
+# coding: utf8
+
+class ListNode(object):
+    def __init__(self, x):
+        self.val = x
+        self.next = None
+
+    def __str__(self):
+        return "ListNode{val=%s, next=%s}" % (self.val, self.next)
+
+    def __repr__(self):
+        return self.__str__() + "@" + hex(id(self))
+
+
+class Solution(object):
+    def sortList(self, head):
+        if head == None or head.next == None:
+            return head
+
+        mid = head
+        tail = head
+        while tail.next != None:
+            tail = tail.next
+            if tail.next != None:
+                tail = tail.next
+                mid = mid.next
+
+        right = mid.next
+        mid.next = None
+
+        head1 = self.sortList(head)
+        head2 = self.sortList(right)
+        return self._merge(head1, head2).next
+
+    def _merge(self, l1, l2):
+        head = ListNode(None)
+        tail = head
+        x = l1
+        y = l2
+
+        while x != None and y != None:
+            if x.val < y.val:
+                tail.next = x
+                tail = x
+                x = x.next
+            else:
+                tail.next = y
+                tail = y
+                y = y.next
+
+        if x != None:
+            tail.next = x
+        if y != None:
+            tail.next = y
+
+        return head
+
+
+if __name__ == "__main__":
+    tmp = None
+    head = None
+    for element in [4, 2, 1, 3]:
+        node = ListNode(element)
+        if head == None:
+            head = node
+            tmp = head
+        else:
+            tmp.next = node
+            tmp = node
+
+    head = Solution().sortList(head)
+    tmp = head
+    while tmp != None:
+        print(tmp)
+        tmp = tmp.next