# Javascript Program To Subtract Two Numbers Represented As Linked Lists

• Last Updated : 03 Jan, 2022

Given two linked lists that represent two large positive numbers. Subtract the smaller number from the larger one and return the difference as a linked list. Note that the input lists may be in any order, but we always need to subtract smaller from the larger ones.
It may be assumed that there are no extra leading zeros in input lists.
Examples:

```Input: l1 = 1 -> 0 -> 0 -> NULL,  l2 = 1 -> NULL
Output: 0->9->9->NULL
Explanation: Number represented as
lists are 100 and 1, so 100 - 1 is 099

Input: l1 = 7-> 8 -> 6 -> NULL,  l2 = 7 -> 8 -> 9 NULL
Output: 3->NULL
Explanation: Number represented as
lists are 786 and  789, so 789 - 786 is 3,
as the smaller value is subtracted from
the larger one.```

Approach: Following are the steps.

1. Calculate sizes of given two linked lists.
2. If sizes are not the same, then append zeros in the smaller linked list.
3. If the size is the same, then follow the below steps:
1. Find the smaller valued linked list.
2. One by one subtract nodes of the smaller-sized linked list from the larger size. Keep track of borrow while subtracting.

Following is the implementation of the above approach.

## Javascript

 ` `

Output:

```0 9 9
```

Complexity Analysis:

• Time complexity: O(n).
As no nested traversal of linked list is needed.
• Auxiliary Space: O(n).
If recursive stack space is taken into consideration O(n) space is needed.

Please refer complete article on Subtract Two Numbers represented as Linked Lists for more details!

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