复杂链表的复制

  题目：复杂链表的复制。一个链表的每个节点，有一个指向next指针指向下一个节点，还有一个random指针指向这个链表中的         一个随机节点或者NULL,现在要求实现复制这个链表，返回复制后的新链表。

解题思路：

   题目中不仅仅要复制指向next指针的节点，还要复制random指针指向这个链表的随机节点或NULL，所以我们要考虑很多的情况，并且还要将一个指针所有的指向都复制下来，如下图给的一个指针：

所以在这个题中分为三步：

（1）先把链表复制一遍，不用管Random指向的随机节点，就变成下图：

将新节点都插入到原来的节点后面：

代码如下：

ComplexNode *pNode = pFirst;
ComplexNode *pNewNode = NULL;
for (pNode = pFirst; pNode; pNode = pNode->pNext->pNext)
	{
		pNewNode = (ComplexNode *)malloc(sizeof(ComplexNode));  //开辟空间，存放新节点
		assert(pNewNode);
		pNewNode->data = pNode->data;                            //将原来节点的值赋给新节点
		pNewNode->pNext = pNode->pNext;                          //插入到原来节点后面
		pNewNode->pRandom = NULL;
		pNode->pNext = pNewNode;
	}

（2）第二步赋值Random指向的随机节点：

从链表头通过原来的节点找节点对应的Random，然后通过原来节点的Random来找到新节点的Random，将新节点指向新节点的Random。如下图：

代码如下：

ComplexNode *pNode = pFirst;
ComplexNode *pNewNode = NULL;
ComplexNode *oldRandom=NULL;
ComplexNode *NewRandom=NULL;
for (pNode = pFirst; pNode; pNode = pNode->pNext->pNext)
	{
		pNewNode = pNode->pNext;      //原来链表的指针域存的是新链表的地址
		oldRandom = pNode->pRandom;   //找到原来链表的Random
		if (oldRandom!=NULL){
			NewRandom = oldRandom->pNext;    //通过原来链表的Random来找新链表的Random
			pNewNode->pRandom = NewRandom;    
		}
		else
                {
			pNewNode->pRandom = NULL;
		}
}

（3）将新链表和原来的链表拆开

将原来的链表链接起来，将新链表链接起来，如下图：

先定义一个指针指向新链表头，然后返回这个指针

代码实现：

ComplexNode *pNode = pFirst;
ComplexNode *pNewNode = NULL;
ComplexNode *pNewFirst=pFirst->pNext ;        //定义一个指针指向新链表头
	for (pNode = pFirst; pNode; pNode = pNode->pNext)
	{
		pNewNode = pNode->pNext;
		pNode->pNext = pNewNode->pNext;
		if (pNode->pNext)
		{
			pNewNode->pNext = pNode->pNext->pNext;
		}
		else
		{
			pNewNode->pNext = NULL;
		}
	}

完整代码实现：

#pragma once
#include<stdio.h>
#include<Windows.h>
#include<stdlib.h>
#include<assert.h>

//定义结构体
typedef struct ComplexNode
{
	int data;
	struct ComplexNode *pNext;
	struct ComplexNode *pRandom;
}ComplexNode;

ComplexNode *CopyNode(ComplexNode * pFirst)
{
	ComplexNode *pNode = pFirst;
	ComplexNode *pNewNode = NULL;
	ComplexNode *oldRandom=NULL;
	ComplexNode *NewRandom=NULL;
	//复制链表
	for (pNode = pFirst; pNode; pNode = pNode->pNext->pNext)
	{
		pNewNode = (ComplexNode *)malloc(sizeof(ComplexNode));
		assert(pNewNode);
		pNewNode->data = pNode->data;
		pNewNode->pNext = pNode->pNext;
		pNewNode->pRandom = NULL;
		pNode->pNext = pNewNode;
	}


	//复制pRandom
	
	for (pNode = pFirst; pNode; pNode = pNode->pNext->pNext)
	{
		pNewNode = pNode->pNext;
		oldRandom = pNode->pRandom;
		if (oldRandom!=NULL){
			NewRandom = oldRandom->pNext;
			pNewNode->pRandom = NewRandom;
		}
		else{
			pNewNode->pRandom = NULL;
		}
	}


	//拆链表
	ComplexNode *pNewFirst=pFirst->pNext ;
	for (pNode = pFirst; pNode; pNode = pNode->pNext)
	{
		pNewNode = pNode->pNext;
		pNode->pNext = pNewNode->pNext;
		if (pNode->pNext)
		{
			pNewNode->pNext = pNode->pNext->pNext;
		}
		else
		{
			pNewNode->pNext = NULL;
		}
	}
	return pNewFirst;
}




//测试部分

ComplexNode	* Buy(int data)
{
	ComplexNode	*pNode = (ComplexNode *)malloc(sizeof(ComplexNode));
	assert(pNode);
	pNode->data = data;
	pNode->pRandom = NULL;
	pNode->pNext = NULL;

	return pNode;
}

void Print(ComplexNode *pFirst)
{
	ComplexNode	*pNode;
	for (pNode = pFirst; pNode; pNode = pNode->pNext) {
		printf("[%d, (%p, %d)] ",
			pNode->data,
			pNode->pRandom,
			pNode->pRandom ? pNode->pRandom->data : 0);
	}
	printf("\n");
}

void TestComplexNode()
{
	ComplexNode	*p1 = Buy(1);
	ComplexNode	*p2 = Buy(2);
	ComplexNode	*p3 = Buy(3);
	ComplexNode	*p4 = Buy(4);

	p1->pNext = p2;
	p2->pNext = p3;
	p3->pNext = p4;

	p1->pRandom = p4;
	p4->pRandom = p1;
	p2->pRandom = p2;

	Print(p1);

	ComplexNode	*pNew = CopyNode(p1);

	Print(pNew);
}