369. Plus One Linked List #182
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Note: In these questions with nodes, graphs and such, I am strongly seeing some aspects of Turing Machines. I am not really well-versed in this topic but that are my observations. |
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| public class PlusOneLinkedList { | ||
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| public ListNode addOne(ListNode head) |
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Can we change the method name to "plusOne" in order to be compatible with LeetCode?
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Quite a smart solution using sentinel node as a dummy head.
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Another sentinel node question. This actually goes together with this. Perhaps as a preparation question for the question 426. |
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Why can't I merge this PR? |
There is a conflict with the code in master. |
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I guess you have used Git commands to merge it. I did not understand what the conflict here was, but I guess the solution you have mentioned would also have worked. |
Yep. We can assume that the Turing machine is the basis of all modern computers. |
Issue.
Let us assume that we are given the head of list like 1-2-3. The operation on this is pretty easy. We just add 1 to the last node, the node without a next node.
What if this number was something like 1-9? Then this operation wouldn't have worked out, as the result would have been 1-10. Hence, we should increment the last digit that is not 9 by 1, then set all the values thereafter to 0. Result is then 2-0. This algorithm also works out for 1-9-9-9, 1-0-9, 8-9-9 and such.
The last possibility is that the given list only contains 9's. Then we should have a some sort of placeholder node
p, whose next node will be our start node. If our head node has the value 9, then the last nine node should bep. In such a situation with 9-9-9-9, this nodepwill obtain the value 1.At the end, we return node
pif its value is not 1, else, we return the head.