面试中常考的单链表处理

#include<stdio.h>
#include<stdlib.h>
#include<assert.h>

struct node
{
	int data;
	struct node *next;
}linknode;

typedef struct node * LinkNode;
LinkNode head = NULL;

LinkNode createNode(int data)
{
	LinkNode node = NULL;
	node = (LinkNode)malloc(sizeof(linknode));
	node->data = data;
	node->next = NULL;
	return node;
}
//在insert函数中返回head后head的值就不会为空,而不返回head时就返回空
LinkNode insert(LinkNode head, int data)
{
	if(head == NULL)
	{
		head = createNode(data);
		return head;
	}
	LinkNode node = NULL;
	node = createNode(data);
	node->data = data;
	node->next = head->next;
	head->next = node;
	return head;
}

void traverse(LinkNode head)
{
	LinkNode p = NULL;
	p = head;
	while( NULL != p)
	{
		printf("%d ", p->data);
		p = p->next;
	}
}

void linkListFree(LinkNode head)
{
	assert(head != NULL);
	LinkNode p = head;
	LinkNode q;
	while( NULL != p)
	{
		q = p->next;
		free(p);
		p = NULL;
		p = q;
	}
}

LinkNode reverse(LinkNode head)
{
	assert(head != NULL);
	LinkNode ptr = createNode(-1);
	ptr->next = head;
	LinkNode p = head->next;
	head->next = NULL;//必须对head->next置空,不然出现循环
	LinkNode q = NULL;
	while(p != NULL)
	{
		q = p->next;
		p->next = ptr->next;
		ptr->next = p;
		p = q;
	}
	return ptr->next;
}

//无头单链表删除节点
void deleteRandomNode(LinkNode p)
{
	assert(p != NULL);
	LinkNode n = p->next;
	if(n != NULL)
	{
		p->data = n->data;
		p->next = n->next;
		free(n);
		n = NULL;
	}
}

//判断两个链表是否相交
bool isIntersect(LinkNode headone, LinkNode headtwo)
{
	assert( (headone!=NULL) && (headtwo!=NULL) );
	LinkNode p = headone;
	while(p->next != NULL)
	{
		p = p->next;
	}
	LinkNode q = headtwo;
	while( (NULL != q) && (q != p) )
	{
		q = q->next;
	}
	if(q == NULL)
		return false;
	return true;
}


//如果相交找到相交的第一个节点
LinkNode firstIntersectNode(LinkNode headone, LinkNode headtwo)
{
	assert( (NULL != headone) && (NULL != headtwo) );
	int lenone = 0, lentwo = 0;
	LinkNode p = headone;
	while(NULL != p)
	{
		lenone++;
		p = p->next;
	}
	p = headtwo;
	while(NULL != p)
	{
		lentwo++;
		p = p->next;
	}
	if(lenone < lentwo)
	{
		p = headtwo;
		for(int i=0; i<(lentwo-lenone); i++)
		{
			p = p->next;
		}
		LinkNode q = headone;
		while( (NULL != p) && (NULL != q) )
		{
			if(p == q)
				return p;
			else
			{
				p = p->next;
				q = q->next;
			}
		}
	}
	else if(lenone > lentwo)
	{
		p = headone;
		for(int i=0; i<(lenone-lentwo); i++)
		{
			p = p->next;
		}
		LinkNode q = headtwo;
		while( (NULL != p) && (NULL != q) )
		{
			if(p == q)
				return p;
			else
			{
				p = p->next;
				q = q->next;
			}
		}
	}
	else
	{
		p = headone;
		LinkNode q = headtwo;
		while( (NULL != p) && (NULL != q) )
		{
			if(p == q)
				return p;
			else
			{
				p = p->next;
				q = q->next;
			}
		}
	}
}


LinkNode createLinkList(int n)
{
	LinkNode h = NULL;
	for(int i=0; i<n; i++)
		h = insert(h, i+1);
	return h;
}

void test()
{
	head = createLinkList(10);
	traverse(head);
	printf("\n");
	LinkNode h = reverse(head);
	LinkNode p = h;
	traverse(h);
}

int main()
{
	test();
	return 0;
}