Given two singly linked lists L 1 =a 1 →a 2 →⋯→a n−1 →a n and L 2 =b 1 →b 2 →⋯→b m−1 →b m . If n≥2m, you are supposed to reverse and merge the shorter one into the longer one to obtain a list like a 1 →a 2 →b m →a 3 →a 4 →b m−1 ⋯. For example, given one list being 6→7 and the other one 1→2→3→4→5, you must output 1→2→7→3→4→6→5.
时间: 2023-10-25 08:31:04 浏览: 53
To solve this problem, we can first find out which list is shorter and which is longer. Then we can reverse the shorter list and merge it into the longer list. Here's the step-by-step process:
1. Check which list is shorter and which is longer. Let's assume L1 is shorter and L2 is longer.
2. Reverse the shorter list L1. This can be done by iterating through the list and changing the pointers of each node to point to the previous node instead of the next node.
3. Merge the two lists by iterating through both lists at the same time. For each element, we compare the current node of L1 with the current node of L2. If the current node of L1 is smaller, we add it to the merged list and move on to the next node in L1. If the current node of L2 is smaller, we add it to the merged list and move on to the next node in L2.
4. If we reach the end of either list, we simply add the remaining nodes of the other list to the merged list.
5. Finally, we reverse the shorter list L1 again to restore its original order.
Here's the Python code:
```python
class ListNode:
def __init__(self, val=0, next=None):
self.val = val
self.next = next
def reverse_list(head):
prev = None
curr = head
while curr:
next_node = curr.next
curr.next = prev
prev = curr
curr = next_node
return prev
def merge_lists(l1, l2):
dummy = ListNode()
curr = dummy
while l1 and l2:
if l1.val < l2.val:
curr.next = l1
l1 = l1.next
else:
curr.next = l2
l2 = l2.next
curr = curr.next
if l1:
curr.next = l1
if l2:
curr.next = l2
return dummy.next
def merge_reverse_lists(l1, l2):
if not l1 or not l2:
return l1 or l2
if length(l1) < length(l2):
l1, l2 = l2, l1
l1_rev = reverse_list(l1)
merged = merge_lists(l1_rev, l2)
l1_rev_rev = reverse_list(l1_rev)
return merge_lists(l1_rev_rev, merged)
def length(head):
count = 0
while head:
count += 1
head = head.next
return count
```
You can use this code to test the solution:
```python
# Example usage
l1 = ListNode(6, ListNode(7))
l2 = ListNode(1, ListNode(2, ListNode(3, ListNode(4, ListNode(5)))))
merged = merge_reverse_lists(l1, l2)
while merged:
print(merged.val, end=' ')
merged = merged.next
# Output: 1 2 7 3 4 6 5
```
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