HDU2594 Simpsons’ Hidden Talents —— KMP next数组

题目链接：https://vjudge.net/problem/HDU-2594

Simpsons’ Hidden Talents

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 10647    Accepted Submission(s): 3722

Problem Description

Homer: Marge, I just figured out a way to discover some of the talents we weren’t aware we had.
Marge: Yeah, what is it?
Homer: Take me for example. I want to find out if I have a talent in politics, OK?
Marge: OK.
Homer: So I take some politician’s name, say Clinton, and try to find the length of the longest prefix
in Clinton’s name that is a suffix in my name. That’s how close I am to being a politician like Clinton
Marge: Why on earth choose the longest prefix that is a suffix???
Homer: Well, our talents are deeply hidden within ourselves, Marge.
Marge: So how close are you?
Homer: 0!
Marge: I’m not surprised.
Homer: But you know, you must have some real math talent hidden deep in you.
Marge: How come?
Homer: Riemann and Marjorie gives 3!!!
Marge: Who the heck is Riemann?
Homer: Never mind.
Write a program that, when given strings s1 and s2, finds the longest prefix of s1 that is a suffix of s2.

 

Input

Input consists of two lines. The first line contains s1 and the second line contains s2. You may assume all letters are in lowercase.

 

Output

Output consists of a single line that contains the longest string that is a prefix of s1 and a suffix of s2, followed by the length of that prefix. If the longest such string is the empty string, then the output should be 0.
The lengths of s1 and s2 will be at most 50000.

 

Sample Input

clinton
homer
riemann
marjorie

 

Sample Output

0
rie 3

 

Source

HDU 2010-05 Programming Contest

 

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题解：

给出两个字符串x和y，求出x的最长前缀，使得该前缀也是y的后缀。

1.把字符串y接到字符串x的后面，中间用个特殊符号隔开。

2.求出新字符串的next[]数组，然后next[len]就是满足该条件的x前缀。

代码如下：

 #include <iostream>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <string>
 #include <vector>
 #include <map>
 #include <set>
 #include <queue>
 #include <sstream>
 #include <algorithm>
 using namespace std;
 typedef long long LL;
 const double eps = 1e-;
 const int INF = 2e9;
 const LL LNF = 9e18;
 const int MOD = 1e9+;
 const int MAXN = 1e5+;

 char x[MAXN], y[MAXN];
 int Next[MAXN];

 void get_next(char x[], int m)
 {
     int i, j;
     j = Next[] = -;
     i = ;
     while(i<m)
     {
         while(j!=- && x[i]!=x[j]) j = Next[j];
         Next[++i] = ++j;
     }
 }

 int main()
 {
     while(scanf("%s%s", x, y)!=EOF)
     {
         int n = strlen(x);
         int m = strlen(y);

         x[n] = '$';
         for(int i = ; i<m; i++)
             x[n++i] = y[i];
         x[n++m] = ;

         int len = n++m;
         get_next(x, len);
         if(Next[len]==) printf("0\n");
         else
         {
             x[Next[len]] = ;
             printf("%s %d\n", x, Next[len]);
         }
     }
 }