Implementation：Sunday 字符串匹配

int sunday(string str, string pattern) {
    int str_len = str.length();
    int pat_len = pattern.length();

    int char_pos[];
    for (int i = ; i<; i++) char_pos[i] = -;

    for (int i = pat_len - ; i>=; i--) char_pos[pattern[i]] = i;

    int i = ;
    int j = ;

    while (i + pat_len <= str_len) {
        while (j < pat_len && str[i] == pattern[j]) {
            i++, j++;
        }
        if (j == pat_len) return i - pat_len;

        int k = i + pat_len - j;
        int p = ;

        while ( k < str_len && (p = char_pos[str[k]]) == -) {
            k += pat_len;
        }

        i = k - p;
        j = ;
    }
    return -;
}

比KMP好理解多了

参考：

http://www.cnblogs.com/lbsong/archive/2012/05/25/2518188.html

简化：

 int sunday(const char* pattern, const char* str) {
     if (pattern == NULL || str == NULL) {
         return -;
     }
     int slen = , plen = ;

     while (pattern[plen] != '\0') plen++;
     while (str[slen] != '\0') slen++;

     int tbl[];
     for (int i=; i<; i++) tbl[i] = -;
     for (int i=; i<plen; i++) tbl[pattern[i]] = i;

     int pi = , si = ;

     while (si < slen) {
         while (str[si] == pattern[pi] && si < slen) si++, pi++;
         if (pi == plen) return si - plen;
         int nidx = plen - pi + si;
         int offset = tbl[str[nidx]];
         si = nidx - offset;
         pi = ;
     }
     return -;
 }