- Think about doing the same thing to an array in O(n) speed and O(1) extra space. It’s kinda hard.
- What makes linked list easier? You can
ignore it's positionin the input array and just assign their
two pointers, one to odd, one to even.
odd pointerpoint to next
even pointerpoint to next
- Move them to next.
odd pointerto connect them together.
- Return the head.
head of a singly linked list, group all the nodes with odd indices together followed by the nodes with even indices, and return the reordered list.
The first node is considered
odd, and the second node is
even, and so on.
Note that the relative order inside both the even and odd groups should remain as it was in the input.
You must solve the problem in
O(1) extra space complexity and
O(n) time complexity.
Input: head = [2,1,3,5,6,4,7]