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merge two sorted lists(leetcode21)

admin 11月 13, 2020 0

Problem
- Example
- Python solution

Problem

Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.

Example

Input:
```
1->2->4, 1->3->4
```
Output:
```
1->1->2->3->4->4
```

Python solution

import sys
import time
import copy

#Definition for singly-linked list.
class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

class Solution:
    def mergeTwoLists(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """

        if not l1:
            return l2
        
        if not l2:
            return l1

        if l1.val <= l2.val:
            root = l1
            l1 = l1.next
        else:
            root = l2
            l2 = l2.next

        l3 = root

        while l1 and l2:
            if l1.val <= l2.val:
                l3.next = l1
                l1 = l1.next
                l3 = l3.next
            else:
                l3.next = l2
                l2 = l2.next
                l3 = l3.next
        
        #Runtime beats 97.38 %
        if l1:
            l3.next = l1
        else:
            l3.next = l2
        result = []
        while root:
            result.append(root.val)
            root = root.next

        return result

def Value2Instance(ValueList):
    Node = ListNode(ValueList[0])
    Root = Node
    for i in range(1, len(ValueList)):
        Node.next = ListNode(ValueList[i])
        Node = Node.next
    return Root

if __name__ == "__main__":
    sys.stdout.write("Input list1: n")
    l1 = list(map(int, list(str(sys.stdin.readline()).strip())))
    sys.stdout.write("Input list2: n")    
    l2 = list(map(int, list(str(sys.stdin.readline()).strip())))
    sys.stdout.write("Result is: n" + str(Solution().mergeTwoLists(Value2Instance(l1), Value2Instance(l2))))