KMP算法

下面是next数组的生成算法:

void GetNextEx(char *T, char *next)

{

          int i=1,j=0; next[1] = 0;

 

          while(i < T[0])

          {

                   if (j == 0 || T[i] == T[j])

                   {

                             ++i; ++j;

 

                             if (T[i] == T[j])

                                      next[i] = next[j];

                             else

                                      next[i] = j;

                   }

                   else j = next[j];

          }

}

下面是KMP算法实现:

int KMP(char* S, char* T, int pos)

{

          int i=pos, j=1;

 

          while (i<S[0] && j<T[0])

          {

                   if (S[i] == T[j]){ ++i; ++j; }

                   else j = next[j]

          }

 

          if (j>T[0]) return i-T[0];

          else return 0;

}

现在是朴素算法:

int Index(char *S, char *T, int pos)

{

          int i=pos,j=1;

          while(i <= S[0] && j<=T[0])

          {

                   if (S[i] == T[j]) { ++i; ++j;}    //如果相同，则继续向后比较

                   else {i = i-j+2; j =1;}  //如果不同，就回溯，重新查找

          }

 

          if (j>T[0]) return i-T[0];

          else return 0;

}