Uva--531(动规,LCS)

本文介绍了一个关于寻找两个文本中最长公共子序列(LCS)的经典问题,并提供了一段C++代码实现。该程序能处理多组输入数据,通过动态规划算法找出最长公共子序列,适用于政治提案等场景。

2014-08-02 16:06:25

2014-08-02 16:05:28

  Compromise 

In a few months the European Currency Union will become a reality. However, to join the club, the Maastricht criteria must be fulfilled, and this is not a trivial task for the countries (maybe except for Luxembourg). To enforce that Germany will fulfill the criteria, our government has so many wonderful options (raise taxes, sell stocks, revalue the gold reserves,...) that it is really hard to choose what to do.

 


Therefore the German government requires a program for the following task:

 


Two politicians each enter their proposal of what to do. The computer then outputs the longest common subsequence of words that occurs in both proposals. As you can see, this is a totally fair compromise (after all, a common sequence of words is something what both people have in mind).

 


Your country needs this program, so your job is to write it for us.

 

Input Specification 

The input file will contain several test cases.

Each test case consists of two texts. Each text is given as a sequence of lower-case words, separated by whitespace, but with no punctuation. Words will be less than 30 characters long. Both texts will contain less than 100 words and will be terminated by a line containing a single '#'.

Input is terminated by end of file.

 

Output Specification 

For each test case, print the longest common subsequence of words occuring in the two texts. If there is more than one such sequence, any one is acceptable. Separate the words by one blank. After the last word, output a newline character.

 

Sample Input 

die einkommen der landwirte
sind fuer die abgeordneten ein buch mit sieben siegeln
um dem abzuhelfen
muessen dringend alle subventionsgesetze verbessert werden
#
die steuern auf vermoegen und einkommen
sollten nach meinung der abgeordneten
nachdruecklich erhoben werden
dazu muessen die kontrollbefugnisse der finanzbehoerden
dringend verbessert werden
#

 

Sample Output 

die einkommen der abgeordneten muessen dringend verbessert werden

思路:经典LCS问题,只不过换了个马甲:单词的形式。
2014-08-02 16:05:28
  Compromise 
In a few months the European Currency Union will become a reality. However, to join the club, the Maastricht criteria must be fulfilled, and this is not a trivial task for the countries (maybe except for Luxembourg). To enforce that Germany will fulfill the criteria, our government has so many wonderful options (raise taxes, sell stocks, revalue the gold reserves,...) that it is really hard to choose what to do.

 


Therefore the German government requires a program for the following task:

 


Two politicians each enter their proposal of what to do. The computer then outputs the longest common subsequence of words that occurs in both proposals. As you can see, this is a totally fair compromise (after all, a common sequence of words is something what both people have in mind).

 


Your country needs this program, so your job is to write it for us.

 

Input Specification 

The input file will contain several test cases.

Each test case consists of two texts. Each text is given as a sequence of lower-case words, separated by whitespace, but with no punctuation. Words will be less than 30 characters long. Both texts will contain less than 100 words and will be terminated by a line containing a single '#'.

Input is terminated by end of file.

 

Output Specification 

For each test case, print the longest common subsequence of words occuring in the two texts. If there is more than one such sequence, any one is acceptable. Separate the words by one blank. After the last word, output a newline character.

 

Sample Input 

die einkommen der landwirte
sind fuer die abgeordneten ein buch mit sieben siegeln
um dem abzuhelfen
muessen dringend alle subventionsgesetze verbessert werden
#
die steuern auf vermoegen und einkommen
sollten nach meinung der abgeordneten
nachdruecklich erhoben werden
dazu muessen die kontrollbefugnisse der finanzbehoerden
dringend verbessert werden
#
 

Sample Output 

die einkommen der abgeordneten muessen dringend verbessert werden

思路:经典LCS问题,只不过换了个马甲:单词的形式。
 1 /*************************************************************************
 2     > File Name: b.cpp
 3     > Author: Nature
 4     > Mail: 564374850@qq.com 
 5     > Created Time: Wed 30 Jul 2014 12:55:24 PM CST
 6 ************************************************************************/
 7 
 8 #include <cstdio>
 9 #include <cstring>
10 #include <cstdlib>
11 #include <cmath>
12 #include <iostream>
13 #include <algorithm>
14 using namespace std;
15 
16 struct Word{
17     char s[35];
18 }w1[105],w2[105];
19 
20 int cnt1 = 0,cnt2 = 0;
21 int path[105][105];
22 int dp[105][105];
23 int head;
24 
25 void Print(int st1,int st2){
26     if(!path[st1][st2])
27         return;
28     if(path[st1][st2] == 3){
29         Print(st1 - 1,st2 - 1);
30         if(!head)
31             printf(" ");
32         printf("%s",w1[st1 - 1].s);
33         head = 0;
34     }
35     else if(path[st1][st2] == 1)
36         Print(st1 - 1,st2);
37     else
38         Print(st1,st2 - 1);
39 }
40 
41 int main(){
42     char tem[35];
43     while(scanf("%s",tem) == 1){
44         cnt1 = cnt2 = 0;
45         memset(dp,0,sizeof(dp));
46         memset(path,0,sizeof(path));
47         if(tem[0] != '#'){
48             strcpy(w1[cnt1++].s,tem);
49             while(scanf("%s",w1[cnt1].s) == 1 && w1[cnt1].s[0] != '#')
50                 ++cnt1;
51         }
52         while(scanf("%s",w2[cnt2].s) == 1 && w2[cnt2].s[0] != '#')
53             ++cnt2;
54         for(int i = 1; i <= cnt1; ++i){
55             for(int j = 1; j <= cnt2; ++j){
56                 if(strcmp(w1[i - 1].s,w2[j - 1].s) == 0){
57                     dp[i][j] = dp[i - 1][j - 1] + 1;
58                     path[i][j] = 3;
59                 }
60                 else if(dp[i - 1][j] > dp[i][j - 1]){
61                     dp[i][j] = dp[i - 1][j];
62                     path[i][j] = 1;
63                 }
64                 else{
65                     dp[i][j] = dp[i][j - 1];
66                     path[i][j] = 2;
67                 }
68             }
69         }
70         head = 1;
71         Print(cnt1,cnt2);
72         printf("\n");
73     }
74     return 0;
75 }

 

转载于:https://www.cnblogs.com/naturepengchen/articles/3887088.html

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