算法之美--3.2.3 KMP算法

不知道看了几遍的kmp，反正到现在都没有弄清楚next[j]的计算和kmp的代码实现，温故而知新，经常回来看看，相信慢慢的就回了

 1 /*!
 2  * \file KMP_算法.cpp
 3  *
 4  * \author ranjiewen
 5  * \date 2017/02/12 16:12
 6  *
 7  */
 8
 9 void preKmp(const char* pattern, int m, int kmpNext[])
10 {
11     int i, j;
12     i = 0;
13     j = kmpNext[0] = -1;
14     while (i<m)
15     {
16         while (j>-1&&pattern[i]!=pattern[j])
17         {
18             j = kmpNext[j];
19         }
20         i++;
21         j++;
22         if (pattern[i]==pattern[j])
23         {
24             kmpNext[i] = kmpNext[j];
25         }
26         else
27         {
28             kmpNext[i] = j;
29         }
30     }
31 }
32
33 #include <iostream>
34 using namespace std;
35 #include <string>
36
37 void KMP(string p, string t)
38 {
39     int m = p.length();
40     int n = t.length();
41     if (m>n)
42     {
43         cerr << "Unsuccessful match!";
44     }
45     const char* x = p.c_str();
46     const char* y = t.c_str();
47
48     int i = 0, j = 0, kmpNext[128];
49     preKmp(x, m, kmpNext);
50
51     i = j = 0;
52     while (i<n)
53     {
54         while (j>-1&&x[j]!=y[i])
55         {
56             j = kmpNext[j];
57         }
58         j++;
59         i++;
60         if (j>=m)
61         {
62             cout << "Matching index found at:" << i - j << endl;
63             j = kmpNext[j];
64         }
65     }
66 }
67
68 int main(int argc, char** argv) {
69
70     string p1 = "abcabcad";
71     string p2 = "adcadcad";
72     string p3 = "ababcaabc";
73     string t = "ctcabcabcadtcaabcabcadat";
74
75     cout << "KMP: " << endl;
76     KMP(p1, t);
77
78     //  cout<<"KMP: "<<endl;
79     //  KMP(p2, t);
80
81     //  cout<<"KMP: ";
82     //  KMP(p3, t);
83
84     return 0;
85 }