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_0328_OddEvenLinkedList.java
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_0328_OddEvenLinkedList.java
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package com.diguage.algorithm.leetcode;
import com.diguage.algorithm.util.ListNode;
import java.util.Arrays;
import java.util.Objects;
import static com.diguage.algorithm.util.ListNodeUtils.build;
import static com.diguage.algorithm.util.ListNodeUtils.printListNode;
/**
* = 328. Odd Even Linked List
*
* https://leetcode.com/problems/odd-even-linked-list/[Odd Even Linked List - LeetCode]
*
* Given a singly linked list, group all odd nodes together followed by the even nodes. Please note here we are talking about the node number and not the value in the nodes.
*
* You should try to do it in place. The program should run in O(1) space complexity and O(nodes) time complexity.
*
* .Example 2:
* [source]
* ----
* Input: 1->2->3->4->5->NULL
* Output: 1->3->5->2->4->NULL
* ----
*
* .Example 2:
* [source]
* ----
* Input: 2->1->3->5->6->4->7->NULL
* Output: 2->3->6->7->1->5->4->NULL
* ----
*
* *Note:*
*
* * The relative order inside both the even and odd groups should remain as it was in the input.
* * The first node is considered odd, the second node even and so on ...
*
* @author D瓜哥, https://www.diguage.com/
* @since 2020-01-12 12:20
*/
public class _0328_OddEvenLinkedList {
/**
* Runtime: 0 ms, faster than 100.00% of Java online submissions for Odd Even Linked List.
*
* Memory Usage: 38 MB, less than 12.50% of Java online submissions for Odd Even Linked List.
*
* Copy from: https://leetcode.com/problems/odd-even-linked-list/solution/[Odd Even Linked List solution - LeetCode]
*/
public ListNode oddEvenList(ListNode head) {
if (Objects.isNull(head)) {
return null;
}
ListNode odd = head;
ListNode even = head.next;
ListNode evenHead = even;
while (Objects.nonNull(even) && Objects.nonNull(even.next)) {
odd.next = even.next;
odd = odd.next;
even.next = odd.next;
even = even.next;
}
odd.next = evenHead;
return head;
}
public static void main(String[] args) {
_0328_OddEvenLinkedList solution = new _0328_OddEvenLinkedList();
ListNode r1 = solution.oddEvenList(build(Arrays.asList(1, 2, 3, 4, 5)));
printListNode(r1);
}
}