PAT_1032: Sharing

To store English words, one method is to use linked lists and store a word letter by letter. To save some space, we may let the words share the same sublist if they share the same suffix. For example, "loading" and "being" are stored as showed in Figure 1.

Figure 1

You are supposed to find the starting position of the common suffix (e.g. the position of "i" in Figure 1).

Input Specification:

Each input file contains one test case. For each case, the first line contains two addresses of nodes and a positive N (<= 10⁵), where the two addresses are the addresses of the first nodes of the two words, and N is the total number of nodes. The address of a node is a 5-digit positive integer, and NULL is represented by -1.

Then N lines follow, each describes a node in the format:

Address Data Next

where Address is the position of the node, Data is the letter contained by this node which is an English letter chosen from {a-z, A-Z}, andNext is the position of the next node.

Output Specification:

For each case, simply output the 5-digit starting position of the common suffix. If the two words have no common suffix, output "-1" instead.

Sample Input 1:

11111 22222 9
67890 i 00002
00010 a 12345
00003 g -1
12345 D 67890
00002 n 00003
22222 B 23456
11111 L 00001
23456 e 67890
00001 o 00010

Sample Output 1:

67890

Sample Input 2:

00001 00002 4
00001 a 10001
10001 s -1
00002 a 10002
10002 t -1

Sample Output 2:

-1

备注：考察链表的题。找两个链表的公共节点，思路是先各扫描两个链表，得到各自的长度L1和L2（假设L1>L2)。然后在长链表处先扫L1-L2个节点，接着两个链表同时开扫，扫到一样的节点就输出。 注意输出格式，要5位的地址，刚开始被略坑一小会。

#include<stdio.h>

typedef struct node
{
	char data;
	int next;
}NODE;
const int MAXSIZE = 100010;
NODE node_list[MAXSIZE];

int main()
{
	int head1,head2,N;
	int i,diff;
	int head,length1,length2,start1,start2;
	scanf("%d %d %d",&head1,&head2,&N);

	for(i=0;i<N;i++)
	{
		int add,next;
		char c;
		scanf("%d %c %d",&add,&c,&next);
		node_list[add].data = c;
		node_list[add].next = next;
	}

	// count length of list1
	head = head1,length1 = 0;
	while(head!=-1)
	{
		head = node_list[head].next;
		length1++;
	}
	// count length of list2
	head = head2,length2 = 0;
	while(head!=-1)
	{
		head = node_list[head].next;
		length2++;
	}

	if(length1==0 || length2==0)
	{
		printf("-1");
		return 0;
	}

	start1 = head1, start2 = head2;
	if(length1>length2)
	{
		diff = length1-length2;
		head = head1;
		for(i=0;i<diff;i++)
			head = node_list[head].next;
		start1 = head;
	}
	else
	{
		diff = length2-length1;
		head = head2;
		for(i=0;i<diff;i++)
			head = node_list[head].next;
		start2 = head;
	}

	while(start1!=-1 && start2!=-1)
	{
		if(start1 == start2)
		{
			printf("%05d",start2);
			break;
		}
		else
		{
			start1 = node_list[start1].next;
			start2 = node_list[start2].next;
		}
	}

	if(start1==-1 && start2==-1)
		printf("-1");

	return 0;
}