golang kmp算法实现

package main

import "fmt"

func genNext(s string) []int {
   sLen := len(s)
   next := make([]int, sLen)
   c := 0
   d := -1
   next[0] = -1
   for c < sLen - 1 {
      if d == -1 || s[c] == s[d] {
         c++
         d++
         if s[c] == s[d] {
            next[c] = next[d]
         }else {
            next[c] = d
         }
      }else {
         d = next[d]
      }
   }
   return next
}

func Kmp(chang string, duan string) int {
   cLen := len(chang)
   dLen := len(duan)
   if dLen == 0 || cLen == 0 {
      return 0
   }
   next := genNext(duan)
   c := -1
   d := -1
   for c < cLen  && d <= dLen  {
      if d == -1 || (chang[c] == duan[d])  {
         c++
         d++
      }else {
            d = next[d]
      }
   }
   if d == dLen {
      return c - dLen
   }
   return 0
}