PAT1032: Sharing (25)

1032. Sharing (25)

时间限制

100 ms

内存限制

65536 kB

代码长度限制

16000 B

判题程序

Standard

作者

CHEN, Yue

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}, and Nextis 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

思路

求两个单词共同后缀开始的位置，标记单词一使用的字母，遍历单词2字母时遇到相同且标记过的字母就是该共同后缀开始的位置。

注：用map或者unorder_map最后一个用例总是超时，而用单纯的数组就能通过，估计map在大量数据情况下插入时间复杂度不好？

代码
最后一个用例超时

#include<iostream>
#include<unordered_map>
#include<string>
using namespace std;
class Node
{
public:
    string address;
    char data;
    string next;
    bool isVisit = false;
};
int main()
{
    string f,s;
    int N;
    while(cin >> f >> s >> N)
    {
       unordered_map<string,Node> nodes;
       for(int i = 0;i < N;i++)
       {
          Node tmp;
          cin >> tmp.address >> tmp.data >> tmp.next;
          nodes.insert(pair<string,Node>(tmp.address,tmp));
       }
       while(f != "-1")
       {
           nodes[f].isVisit = true;
           f = nodes[f].next;
       }

       while(s != "-1" && !nodes[s].isVisit)
       {
           s = nodes[s].next;
       }
       if(nodes[s].isVisit)
        cout << s << endl;
       else
        cout << "-1" << endl;
    }
}

AC的代码

#include <cstdio>  
#include <cstring>  
using namespace std;  
  
int  node[100000],temp[100000];  
  
int main()  
{  
    memset(node,-1,sizeof(node));  
  
    int start1,start2,n,from,to;  
    char s[2];  
  
    scanf("%d %d %d",&start1,&start2,&n);  
    for( int i=0; i<n; i++)  
    {  
        scanf("%d %s %d",&from,s,&to);  
        node[from] = to;  
    }  
    while(start1 != -1)  
    {  
        temp[start1] = 1;  
        start1 = node[start1];  
    }  
    while(start2 != -1)  
    {  
        if(temp[start2])  
        {  
            printf("%05d
",start2);  
            return 0;  
        }  
        start2 = node[start2];  
    }  
    printf("-1
");  
    return 0;  
}