Golang | Leetcode Golang题解之第143题重排链表

题目：

题解：

func middleNode(head *ListNode) *ListNode {
    slow, fast := head, head
    for fast.Next != nil && fast.Next.Next != nil {
        slow = slow.Next
        fast = fast.Next.Next
    }
    return slow
}
 
func reverseList(head *ListNode) *ListNode {
    var prev, cur *ListNode = nil, head
    for cur != nil {
        nextTmp := cur.Next
        cur.Next = prev
        prev = cur
        cur = nextTmp
    }
    return prev
}
 
func mergeList(l1, l2 *ListNode) {
    var l1Tmp, l2Tmp *ListNode
    for l1 != nil && l2 != nil {
        l1Tmp = l1.Next
        l2Tmp = l2.Next
 
        l1.Next = l2
        l1 = l1Tmp
 
        l2.Next = l1
        l2 = l2Tmp
    }
}
 
func reorderList(head *ListNode) {
    if head == nil {
        return
    }
    mid := middleNode(head)
    l1 := head
    l2 := mid.Next
    mid.Next = nil
    l2 = reverseList(l2)
    mergeList(l1, l2)
}