扩展kmp模板

Posted 2020-10-02 ygeloutingyu

参考博客: https://wenku.baidu.com/view/8e9ebefb0242a8956bece4b3.html

　　　　 http://www.cnblogs.com/Rlemon/archive/2013/06/26/3157574.html

 

代码:

 1 #include <iostream>
 2 #include <stdio.h>
 3 #include <string.h>
 4 using namespace std;
 5 
 6 const int MAXN = 1e5 + 10;
 7 char str1[MAXN], str2[MAXN]; //str1为主串,str2为模式串
 8 int exnext[MAXN], extend[MAXN], n, m;
 9 
10 void get_exnext(void){
11     exnext[0] = m;
12     int j = 0, k = 1; //k是使p最大的i
13     while(j + 1 < m && str2[j] == str2[j + 1]) j++;
14     exnext[1] = j;
15     for(int i = 2; i < m; i++){
16         int p = exnext[k] + k - 1; //p为当前匹配最远的位置
17         int l = exnext[i - k]; //[k,p]匹配[0,exnext[k]-1],所以[i,p]匹配[i-k,exnext[k]-1],[i-k,i-k+l]匹配[0,l]
18         if(i + l < p + 1) exnext[i] = l;
19         else{
20             j = max(0, p - i + 1);
21             while(i + j < m && str2[i + j] == str2[j]) j++;
22             exnext[i] = j;
23             k = i;
24         }
25     }
26 }
27 
28 void ex_kmp(void){
29     get_exnext();
30     int j = 0, k = 0;
31     while(j < n && j < m && str1[j] == str2[j]) j++;
32     extend[0] = j;
33     for(int i = 1; i < n; i++){
34         int p = extend[k] + k - 1;
35         int l = exnext[i - k];
36         if(i + l < p + 1) extend[i] = l;
37         else{
38             j = max(0, p - i + 1);
39             while(i + j < n && j < m && str1[i + j] == str2[j]) j++;
40             extend[i] = j;
41             k = i;
42         }
43     }
44 }
45 
46 int main(void){
47     scanf("%s%s", str1, str2);
48     n = strlen(str1);
49     m = strlen(str2);
50     ex_kmp();
51     for(int i = 0; i < m; i++){
52         cout << exnext[i] << " ";
53     }
54     cout << endl;
55     for(int i = 0; i < n; i++){
56         cout << extend[i] << " ";
57     }
58     cout << endl;
59     return 0;
60 }

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