题目

旋转链表

问题:

给定一个链表，旋转链表，将链表每个节点向右移动k个位置，其中k是非负数。

示例:

输入:1->2->3->4->5->null 和 k=2
输出:4->5->1->2->3->null

代码：

/**
public class SingNode {
    public var value : Int
    public var nextNode: SingNode?
    
    public init(value:Int) {
        self.value = value
    }
}

extension SingNode : CustomStringConvertible {
    public var description: String {
        var string = "\(value)"
        var node = self.nextNode
        
        while node != nil {
            string = string + " -- " + "\(node!.value)"
            node = node?.nextNode
        }
        return string
    }
}
 **/
    func rotateRightNode(_ l1:SingNode?, _ right:Int) -> SingNode? {
        if l1 == nil {
            return nil
        }
        
        var total = 0
        var p = l1
        var last = p
        
        while p != nil {
            total += 1
            last = p
            p = p?.nextNode
        }

        let rightIndex = right%total
        if rightIndex == 0  {
            return l1
        }
        
        let dummyNode = SingNode.init(value: 0)
        dummyNode.nextNode = l1
        p = dummyNode
        
        for _ in 0..<rightIndex {
            p = p?.nextNode
        }
        let ret = p?.nextNode
        p?.nextNode = nil
        last?.nextNode = dummyNode.nextNode
        return ret
    }