Linux GCC下strstr的实现以及一个简单的Kmp算法的接口

 1 char *strstr(const char*s1,const char*s2)
 2 {
 3     const char*p=s1;
 4     const size_t len=strlen(s2);
 5     for(;(p=strchr(p,*s2))!=0;p++)
 6     {
 7         if(strncmp(p,s2,len)==0)
 8             return (char*)p;
 9     }
10     return(0);
11 }

  1 #include <string.h>
  2 #include <stdio.h>
  3 
  4 #define LIB_MATCH_NUM  5
  5 #define LIB_STRING_LEN 40
  6 
  7 char lib_match[LIB_MATCH_NUM][LIB_STRING_LEN] =
  8 {
  9     "www.baidu.comw",
 10     "www.google.com",
 11     "www",
 12     "baidu.com",
 13     "lualu",
 14 };
 15 
 16 int lib_match_len[LIB_MATCH_NUM];
 17 
 18 int lib_match_next[LIB_MATCH_NUM][LIB_STRING_LEN + 1] = {0};
 19 
 20 
 21 void get_next();
 22 
 23 void lib_match_init()
 24 {
 25     memset(lib_match_len,0,sizeof(lib_match_len));
 26     int i;
 27     for(i = 0; i < LIB_MATCH_NUM; i++)
 28     {
 29         lib_match_len[i] = strlen(lib_match[i]); 
 30     }
 31 
 32     get_next(); // init next array 
 33 }
 34 
 35 void get_next()
 36 {
 37     int i,j,k;
 38 
 39     for(i = 0; i < LIB_MATCH_NUM; i++)
 40     {
 41         
 42         lib_match_next[i][0] = 0;
 43         lib_match_next[i][1] = 0;
 44         
 45         k = 0; //point to the last next[j]
 46         int len = lib_match_len[i];
 47 
 48         for( j = 1; j < len; j++)
 49         {//j start from 1 because next start from 2
 50             while(k > 0 && lib_match[i][j] != lib_match[i][k])
 51             {
 52                 k = lib_match_next[i][k];
 53             }
 54 
 55             if(lib_match[i][j] == lib_match[i][k])
 56             {//s[j] == s[next[k]] next[i+1] = next[i] +1
 57                 k++; 
 58             }
 59 
 60             lib_match_next[i][j+1] = k;
 61         }
 62     
 63     }
 64 
 65 }
 66 
 67 int lib_search(char *orignal,int len)
 68 {
 69     int i,j,k;
 70     
 71     for(i = 0; i < LIB_MATCH_NUM; i++)
 72     {
 73         char *tmp = orignal; // match each model need to start from the first
 74         k = 0; // k start from the last next array
 75 
 76         for(j = 0; j < len; j++)
 77         {
 78             
 79             while( k > 0 && tmp[j] != lib_match[i][k])
 80             {
 81                 k = lib_match_next[i][k];
 82             }
 83 
 84             if(tmp[j] == lib_match[i][k])
 85             {
 86                 k++;
 87             }
 88 
 89             if(k == lib_match_len[i])
 90             {
 91                 printf("match the model string %d : %s\n", i,lib_match[i]);
 92                 printf("match at the position  :%d\n\n", j - lib_match_len[i] + 1);
 93                 
 94                 // here can return the i to know which model string have been matched
 95             
 96                 k = lib_match_next[i][k]; //to match another this model string 
 97             }
 98 
 99         }
100 
101     }    
102 
103     return 0;
104 }
105 
106 void print_next()
107 {
108     int i,j;
109     
110     for(i = 0; i < LIB_MATCH_NUM; i++)
111     {
112         printf("model string : %s \n",lib_match[i]);
113         printf("next array:");
114         for(j = 0; j < lib_match_len[i]+1;j++)
115         {
116             printf(" %d",lib_match_next[i][j]);
117         }
118         printf("\n\n");
119     }
120 }
121 
122 
123 int main()
124 {
125     char orignal[40];
126         
127     lib_match_init();
128 
129     print_next();
130 
131     while(1)
132     {    
133 
134         scanf("%s",orignal);
135 
136         if(strcmp(orignal,"0") == 0)
137         {
138             return 0;
139         }
140 
141         lib_search(orignal,strlen(orignal));
142     }
143 
144     return 0;
145 
146 }