KMP算法

这个KMP算法效率有点问题。有个地方又回溯了~Find out and fix it.
>> >>>>>>>>>>Okey。小哥，怎么样了？哥们写得一手好字啊~
这是修正后的代码：
voidkmpNextEx(char *pattern, int *next, int len) {
   int i = 1;
   int j = -1;
 
   next[0]= -1;
 
   while(i < len) {
      if(j == -1 || pattern[i - 1] == pattern[j]) {
        /* 注意这里：如果发现与上一次匹配的值相同，则直接将上一次匹配的值赋予给新的
         * next[i]，这样可以改进如果Pattern有重复字符出现的情况
         */
        if(pattern[i - 1] != pattern[j - 1]) {
           next[i]= j + 1;
        }else {
           next[i]= next[j];
        }
        ++j;
        ++i;
      }
      else {
        j= next[j];
      }
   }
}
图片
 
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
voidkmpNext(char*, int*, int);
intkmpIndexOf(char*, char*);
intbfIndexOf(char*, char*);
 
int main(int argc, char*argv[]) {
   char *s1 = "2aaaaaaaaaaaaaaasdfasdf134123asdffffffo1asd1234\
      ffffasdf213fvzazxcnvjklnaskld./zca;sdjkfjaiou21o3elan'[ \
      123454154sa4df6548210ykzht4341bwasd1231234239r \
      4sauioj9j91u8hdjkadu9891nkjklfau12 \
      134j0zhcjkvuiuizuionvjjksanfjih2bjkbmzjkxvhiannzjkvjkla \
      4=01293=0ykzht4341bwasd123123423l";
   char *pat = "0ykzht4341bwasd123123423l";
   char *answer = (char*)malloc(sizeof(pat) + 1);
 
   printf("Patter:\t%s\n", pat);
   printf("%-20s%d\n", "ByKMP:", kmpIndex(s1, pat));
   strncpy(answer,s1 + kmpIndex(s1, pat), strlen(pat));
   answer[strlen(pat)]= '\0';
   printf("Answer:\t%s\n", answer);
   getchar();
 
   return 0;
}
 
intkmpIndex(char *strsrc, char*pattern) {
   int *next = (int*)malloc(sizeof(int) *strlen(pattern));
 
   int strsrcLen = strlen(strsrc);
   int patLen = strlen(pattern);
 
   int i = 0;
   int j = 0;
 
   kmpNext(pattern,next, strlen(pattern));
  
   while(i < strsrcLen && j < patLen) {
      if(j == -1 || strsrc[i] == pattern[j]) {
        //printf("%d\n", i);
        ++i;
        ++j;
      }
      else {
        j= next[j] - 1;
      }
   }
 
   if(j >= patLen) {
      return i - patLen;
   }
   else {
      return -1;
   }
}
 
voidkmpNext(char *pattern, int*next, int len) {
   int i = 2;
 
   int j = 1;
   int count = 0;
  
   next[0]= 0;
   next[1]= 1;
 
   while(i < len) {
      j= 0;
      count= 0;
      while(pattern[j] == pattern[i - j - 1] && j< i - 1) {
        count++;
        ++j;
      }
      if(count == 0) {
        count= 1;
      }
      next[i]= count;
      ++i;
   }
  
}