无头单链表面试题 总结

其他 2018-09-11 20:18:48 阅读次数: 0

 链表面试题总结：

  • 逆序打印单项链表     递归实现

  • 在无头单链表的非头结点前插入一个元素

  • 约瑟夫环问题

       首先了解约瑟夫环是什么：约瑟夫环（约瑟夫问题）是一个数学的应用问题：已知n个人（以编号1，2，3...n分别表示）围坐在一张圆桌周围。从编号为k的人开始报数，数到m的那个人出列；他的下一个人又从1开始报数，数到m的那个人又出列；依此规律重复下去，直到圆桌周围的人全部出列。通常解决这类问题时我们把编号从0~n-1，最后  结果+1即为原问题的解。

  • 合并两个有序列表 

创建一个新链表，将两个链表遍历，小的放进新链表中，直到一个为空，将剩余放进新链表中

  • 查找单链表的中间节点，要求只能遍历一次链表

运用两个快慢指针解决，

fast每次走两步，

slow每次走一步，

当fast走到尾时，

slow指向的是中间节点

因为slow走的是fast的一半。

  • 查找单链表的倒数第k个节点，要求只能遍历一次链表 

先将fast走k步，后slow与fast同时走，当fast走到尾时，slow指向的是倒数第k个

  • 判断链表是否带环

当有环时，fast总会与slow相遇，否则fast会走向空。

  • 求环的长度

  • 求环的入口点

  • 判断两条单项链表是否相交

  • 找到交点

以下是代码实现：

linklist.h 

#ifndef __LINKLIST_H__ 
#define __LINKLIST_H__ 

typedef int DataType;
typedef struct Node
{
	DataType data;
	struct Node* next;
}Node, *pNode, List, *pList;

void InitLinkList(pList* pplist);
pNode BuyNode(DataType d);
void DestroyLinkList(pList* pplist);      // 释放链表
void PushBack(pList* pplist, DataType d);	
void PopBack(pList* pplist);				//尾删
void PushFront(pList* pplist, DataType d);
void PopFront(pList* pplist);
pNode Find(pList plist, DataType d);
void Insert(pList* pplist, pNode pos, DataType d);//在指定位置之前插入一个值 
void Erase(pList* pplist, pNode pos);//指定位置删除 
void Remove(pList* pplist, DataType d);
void RemoveAll(pList* pplist, DataType d);
void EraseNotTailNode(pNode pos);
void PrintLinkList(pList plist);
int GetListLength(pList plist);





//链表面试题 
void PrintTailToHead(pList plist);   // 逆序打印单项链表 
void InsertFrontNode(pNode pos, DataType x);//在无头单链表的非头结点前插入一个元素 
void JosephCycle(pList* pplist, int k); //约瑟夫环问题 
pList Merge(pList* p1, pList* p2); //合并两个有序列表 
pNode FindMidNode(pList plist); //查找单链表的中间节点，要求只能遍历一次链表
pNode FindKNode(pList plist, int k); //查找单链表的倒数第k个节点，要求只能遍历一次链表 
void MakeRing(pList* pplist); //建环
pNode CheckCircle(pList plist);//判断链表是否带环 
int GetCircleLength(pNode meet); //求环的长度 
pNode GetCycleEntryNode(pList plist, pNode meet); //求环的入口点 
int CheckCross(pList list1, pList list2); //判断两条单项链表是否相交 
pNode GetCrossNode(pList list1, pList list2);//找到交点


#endif //__LINKLIST_H__

 linklist.c

#define _CRT_SECURE_NO_WARNINGS 1
#include "linklist.h"
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>

void PrintLinkList(pList plist)
{
	pNode cur = plist;
	if (cur == NULL)
	{
		printf("empty");
	}
	else
	{
		while (cur)
		{
			printf("%d-> ", cur->data);
			cur = cur->next;
		}
		printf("over");
	}
	printf("\n");
}


void InitLinkList(pList* pplist)
{
	assert(pplist != NULL);
	
	(*pplist) = NULL;

}


pNode BuyNode(DataType d)
{
	pNode NewNode = NULL;
	NewNode = (pNode)malloc(sizeof(Node));
	if (NewNode == NULL)
	{
		printf("开创失败");
		exit(EXIT_FAILURE);
	}
	else
	{
		NewNode->data = d;
		NewNode->next = NULL;
	}
	
	return NewNode;
}

void DestroyLinkList(pList* pplist)
{
	pNode cur = *pplist;
	pNode del = NULL;
	assert(pplist);
	while (cur)
	{
		del = cur;
		cur = cur->next;
		free(del);
		del = NULL;
	}
}

void PushBack(pList* pplist, DataType d)
{
	assert(pplist);
	pNode NewNode = BuyNode(d);
	pNode cur = *pplist;
	if (cur == NULL)
	{
		*pplist = NewNode;
		return;	
	}
	else
	{
		while (cur->next != NULL)
		{
			cur = cur->next;
		}
		cur->next = NewNode;
	}
}


void PopBack(pList* pplist)
{
	assert(pplist != NULL);
	pNode cur = *pplist;
	if (cur->next == NULL)
	{
		free(cur);
		*pplist = NULL;
	}
	while (cur->next->next != NULL)
	{
		cur = cur->next;
	}
	free(cur->next);
	cur->next = NULL;

}

void PushFront(pList* pplist, DataType d)
{
	assert(pplist != NULL);
	pNode cur = BuyNode(d); 
	cur->next = *pplist;
	*pplist = cur;
}

void PopFront(pList* pplist)
{
	assert(pplist);
	if (*pplist == NULL)
	{
		return;
	}
	pNode del = NULL;
	del = *pplist;
	*pplist = del->next;
	free(del);

}

pNode Find(pList plist, DataType d)
{
	pNode cur = plist;
	while (cur->next != NULL)
	{
		if (cur->data == d)
		{
			return cur;
		}
		else
		{
			cur = cur->next;
		}
	}
	return NULL;
}

void Insert(pList* pplist, pNode pos, DataType d)
{
	assert(pplist);
	pNode NewNode = BuyNode(d);
	pNode cur = *pplist;
	if (*pplist == pos)
	{
		PushFront(pplist, d);
	}
	else
	{
		while (cur &&cur->next != pos)
		{
			cur = cur->next;
		}
		NewNode->next = pos;
		cur->next = NewNode;

	}
	
}

void Erase(pList* pplist, pNode pos)
{
	assert(pplist);
	if (*pplist == NULL)
	{
		return;
	}
	pNode cur = *pplist;
	
	while (cur&&cur->next != pos)
	{
		cur = cur->next;
	}
	cur->next = pos->next;
	free(pos);


}

void Remove(pList* pplist, DataType d)
{
	assert(pplist);
	pNode del = *pplist;
	while(del->data != d)
	{	
		del = del->next;
	}
	pNode cur = *pplist;
	while (cur->next != del)
	{
		cur = cur->next;
	}
	cur->next = del->next;
	free(del);
	
}

void RemoveAll(pList* pplist, DataType d)
{
	assert(pplist);
	pNode cur = *pplist;
	pNode pre = *pplist;
	
	while (cur != NULL)
	{
		if (cur->data == d)
		{
			pNode del = cur;
			pre->next = cur->next;
			cur = pre->next;
			free(del);
		}
		else
		{
			pre = cur;
			cur = cur->next;
		}
	}
	
}

void EraseNotTailNode(pNode pos)
{
	pNode cur = pos;
	if (cur == NULL || cur->next == NULL)
		return;
	cur = pos->next;
	pos->data = cur->data;
	pos->next = cur->next;
	free(cur);
}


int GetListLength(pList plist)
{
	assert(plist);
	pNode cur = plist;
	int length = 0;
	while (cur != NULL)
	{
		length++;
		cur = cur->next;
	}
	return length;
}

//
//
//递
//
//
//归
//
//

void PrintTailToHead(pList plist)  
{
	if (plist != NULL)
	{
		if (plist->next != NULL)
		{
			PrintTailToHead(plist->next);
		}
		printf("%d ", plist->data);
	}
	
}

void InsertFrontNode(pNode pos, DataType x)
{
	pNode NewNode = BuyNode(x);     //插入分两步 
	NewNode->next = pos->next;      //先与后面相连
	pos->next = NewNode;				//再将之连到pos->next
	DataType tmp = 0;
	tmp = pos->data;
	pos->data = NewNode->data;
	NewNode->data = tmp;
	
}


void JosephCycle(pList* pplist, int k)
{
	assert(pplist);
	pNode tou = *pplist;
	pNode cur = *pplist;
	pNode pre = NULL;
	while (tou->next != NULL)      //建环
	{
		tou = tou->next;
	}
	tou->next = *pplist;



	while (cur->next != cur)
	{
		for (int i = 1; i <= k; i++)       //循环k次
		{
			pre = cur;
			cur = cur->next;
		}
		pre->next = cur->next;     //将cur前后2个节点相连
		free(cur);
		cur = pre->next;				//再从pre下一个报数
	}
	cur->next = NULL;
	
}






pNode FindMidNode(pList plist)
{
	pNode slow = plist;
	pNode fast = plist;
	while (fast != NULL&&fast->next != NULL)
	{
		slow = slow->next;
		fast = fast->next->next;
	}
	return slow;
}

pNode FindKNode(pList plist, int k)
{
	pNode first = plist;
	pNode second = plist;
	while (k--)
	{
		first = first->next;
	}
	while (first != NULL)
	{
		first = first->next;
		second = second->next;
	}

	return second;
}

List* Merge(pList* p1, pList* p2)
{
	assert(p1);
	assert(p2);
	List* list = NULL;
	pNode cur1 = p1;
	pNode cur2 = p2;
	while (cur1 != NULL&&cur2 != NULL)
	{
		if (cur1->data < cur2->data)
		{
			PushBack(&list, cur1->data);
			cur1 = cur1->next;
		}
		else
		{
			PushBack(&list, cur2->data);
			cur2 = cur2->next;
		}
	}
	while (cur1 != NULL)
	{
		PushBack(&list, cur1->data);
		cur1 = cur1->next;
	}
	while (cur2 != NULL)
	{
		PushBack(&list, cur2->data);
		cur2 = cur2->next;
	}
	return list;

}
void MakeRing(pList* pplist)
{
	assert(pplist);
	pNode cur = *pplist;
	pNode per = *pplist;
	while (cur->next!=NULL)
	{
		cur = cur->next;
	}
	cur->next = per->next->next;
}


pNode CheckCircle(pList plist)//判断链表是否带环 
{
	assert(plist);
	pNode fast = NULL;
	pNode slow = NULL;
	fast = plist;
	slow = plist;
	while (1)
	{
		fast = fast->next->next;
		slow = slow->next;
		if (fast->next == NULL)
			return NULL;
		if (fast == slow)
			return slow;
	}
}


int GetCircleLength(pNode meet) //求环的长度               给的是相遇点
{
	pNode cur = meet;
	int count = 1;
	while (cur->next != meet)
	{
		count++;
		cur = cur->next;
	}
	return count;
}


pNode GetCycleEntryNode(pList plist, pNode meet)//求环的入口点 
//相遇点到入口点的距离      等于      链表从头走到入口点的位置
{
	assert(plist);
	pNode cur = plist;
	pNode tail = meet;
	while (cur != tail)
	{
		cur = cur->next;
		tail = tail->next;
	}
	return cur;
}
int CheckCross(pList list1, pList list2) //判断两条单项链表是否相交 
{
	pNode cur1 = list1;
	pNode cur2 = list2;
	while (cur1->next != NULL)
	{
		cur1 = cur1->next;
	}
	while (cur2->next != NULL)
	{
		cur2 = cur2->next;
	}
	if (cur1 == cur2)
		return 1;
	else
		return 0;
}
pNode GetCrossNode(pList list1, pList list2)
{
	assert(list1);
	assert(list2);

	int len1 = GetListLength(list1);
	int len2 = GetListLength(list2);
	pNode cur = list1;
	pNode tmp = list2;
	if (len1 > len2)
	{
		for (int i = 0; i < len1 - len2; i++)
		{
			cur = cur->next;
		}
	}

	if (len1 < len2)
	{
		for (int i = 0; i < len2 - len1; i++)
		{
			tmp = tmp->next;
		}
	}


	while (list1 != NULL)
	{
		if (list1 == list2)
			return list1;
		list1 = list1->next;
		list2 = list2->next;
	}
	return NULL;
}

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