C语言字符串匹配函数建议收藏

  1 #include <stdio.h>
  2 #include <stdlib.h>
  3 #include <string.h>
  4 #include <assert.h>
  5 #include <time.h>
  6 
  7 /*
  8 pattern:
  9 pos:
 10 */
 11 
 12 static int badShift[256];
 13 
 14 
 15 static int goodPostfixLastPos(const char *pattern,int pos)
 16 {
 17 #define _break(flag) if(flag){ break;}
 18 
 19     int flag = 0;
 20     int len = strlen(pattern);
 21     int postFix_len = len - pos;
 22     int postFix_position = pos;
 23     int initStart = pos - postFix_len;
 24     int last_start = 0;
 25     while(postFix_len)
 26     {
 27         last_start = (postFix_position == pos) ?initStart:0;
 28         int postFix_start = postFix_position;
 29         for(;last_start>=0 && postFix_start<len;last_start++,postFix_start++)
 30         {
 31             flag = (pattern[last_start] == pattern[postFix_start]);
 32             _break(!flag);
 33 
 34         }
 35 
 36         _break(flag);
 37         if(initStart >= 0)
 38         {
 39             initStart--;
 40         }
 41         else
 42         {
 43             postFix_position++;
 44             postFix_len--;
 45         }
 46     }
 47 
 48     return flag?last_start-1:-1;
 49 }
 50 
 51 static int *calc_goodPostfixShift(const char *pattern,int *goodShift)
 52 {
 53     int len = strlen(pattern);
 54     for(int i=0;i<len;i++)
 55     {
 56         goodShift[i] = len - goodPostfixLastPos(pattern,i) - 1;
 57     }
 58 
 59     return goodShift;
 60 }
 61 
 62 static int *clac_badcharShift(const char *ptrn)
 63 {
 64     int i;
 65     int pLen = strlen(ptrn);
 66 
 67     for(i = 0; i < 256; i++)
 68     {
 69         *(badShift+i) = pLen;
 70     }
 71 
 72     while(pLen != 0)
 73     {
 74         *(badShift+(unsigned char)*ptrn++) = --pLen;
 75     }
 76 
 77     return badShift;
 78 }
 79 
 80 int BMSearch(const char *str,const char *pattern)
 81 {
 82     
 83     int goodShift[strlen(pattern)];
 84     int len1 = strlen(str);
 85     int len2 = strlen(pattern);
 86 
 87     clac_badcharShift(pattern);
 88     calc_goodPostfixShift(pattern,goodShift);
 89     for(int i=len2 - 1;i<len1;)
 90     {
 91         int start = i;
 92         int pos_pattern = len2 - 1;
 93         for(;pos_pattern>=0;pos_pattern--,start--)
 94         {
 95             if(str[start] != pattern[pos_pattern])
 96             {
 97                 break;
 98             }
 99         }
100         if(pos_pattern < 0)
101         {
102             return start + 1;
103         }
104 
105         if(pos_pattern == (len2 - 1))
106         {
107             i += badShift[str[start]];
108         }
109         else
110         {
111             i += goodShift[pos_pattern + 1];
112         }
113     }
114 
115     return -1;
116 }