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 

 

/*!* \file KMP_算法.cpp** \author ranjiewen* \date 2017/02/12 16:12**/void preKmp(const char* pattern, int m, int kmpNext[])  //和GetNextval等价{    int i, j;    i = 0;    j = kmpNext[0] = -1;    while (i
     
      -1 && pattern[i] != pattern[j]) // i为后缀，j为前缀        {            j = kmpNext[j];        }        i++;        j++;        if (pattern[i] == pattern[j])        {            kmpNext[i] = kmpNext[j];        }        else        {            kmpNext[i] = j;        }    }}#include 
      
       using namespace std;#include 
       
        void KMP(string p, string t){    int m = p.length();    int n = t.length();    if (m>n)    {        cerr << "Unsuccessful match!";    }    const char* x = p.c_str();    const char* y = t.c_str();    int i = 0, j = 0, kmpNext[128];    preKmp(x, m, kmpNext);    i = j = 0;    while (i
        
         -1 && x[j] != y[i])        {            j = kmpNext[j];        }        j++;        i++;        if (j >= m)        {            cout << "Matching index found at:" << i - j << endl;            j = kmpNext[j];        }    }}int main(int argc, char** argv) {    string p1 = "abcabcad";    string p2 = "adcadcad";    string p3 = "ababcaabc";    string t = "ctcabcabcadtcaabcabcadat";    cout << "KMP: " << endl;    KMP(p1, t);    //  cout<<"KMP: "<
        
       
      
     

•  以后kmp算法都按照这样写

void GetNext(char* p, int next[]){    int pLen = strlen(p);    next[0] = -1;    int k = -1;    int j = 0;    while (j < pLen - 1) //j

 有这样写的，else效果就是j==-1的时候

while (Text[i] != '\0' && Pattern[j] != '\0')    {        if (Text[i] == Pattern[j])        {            ++i;// 继续比较后继字符            ++j;        }        else        {            index += j - next[j];            if (next[j] != -1)                j = next[j];// 模式串向右移动            else            {                j = 0;                ++i;            }        }    }//while