#if 0  ///strcpy字串賦值函式實現
///法1
/*char my_strcpy(char *dest, const char *src)
 {
    assert(dest!=NULL && src != NULL);
    while((*dest++ = *src++) != '\0');
 }*/
 ///法2
 void my_strcpy(char* Dest, const char *Src)
 {
     assert((Dest!= NULL)&&(Src!=NULL));
     while((*Dest = *Src)!='\0'){
         Dest++;
         Src++;
     }
 }
 int main()
 {
     int a=3;
     char dest[]="abc";
     ///char *dest="abc"; ///error 這樣傳過去的是個地址，不能把字串賦值再指標中  且字元常量存放在常量區
     //char src[]="def";
     char *src="def";  ///can use

     my_strcpy(dest,src);
     printf("%s\n",dest);

     return 0;
 }
 #endif

 #if 0   ///strcat 字串追加函式實現
 char *my_strcat(char *dest, const char *stc)
{
    char *temp;

    assert(dest!=NULL && stc != NULL);
    while(*dest)
    dest++;
    while((*dest++ = *stc++) != '\0');

    return temp;
}
int main()
 {
     int a=3;
     //char dest[20]="abc";
     char dest[]="abc";
     char *src="def";  ///can use

     my_strcat(dest,src);
     printf("%s\n",dest);
     return 0;
 }
 #endif // 1

#if 0  ///strstr字串中子串查詢函式實現
/*char my_strstr(char *str, char c)  ///no use
{
    for(; *str != c; str++)
    if(*str == '\0')
        return NULL;
    else{
          printf("str=%s\n",str);
          return str;
    }
}*/
const char *my_strstr(char *str, char *sub_str)
{
    int i;
    //assert(NULL != str && NULL != sub_str);
    if(str==NULL||NULL==sub_str)
    {
        return str;
    }
    const char *bp=str;
    const char *sp=sub_str;

    ///法1 更清晰
    for( i= 0; bp[i] != '\0'; i++)
    {
        int tem = i; //tem保留主串中的起始判斷下標位置
        int j = 0;
        while(bp[i++] == sp[j++])
        {
            if(sp[j] == '\0')
            {
                return &bp[tem];
            }
        }
        i = tem;
    }
    ///法2 can use
    //while(*str)
    //{
       // bp=str;
        //sp=sub_str;
        //do{
            //if(!*sp)
                //return str;
            //}while(*bp++==*sp++);
        //str+=1;
    //}

    ///查看出現次數
    //int sum=0,ln=strlen(sub_str);
    //while(str=strstr(str,sub_str)){
      //  sum++;
        //str+=ln;
    //}
    //return sum;

    return NULL;
}

int main()
{
     const char dest[]="abcefg";
      char *src="ce";  ///can use
     //char *dest="abcefg";
     //char src='c';  ///no use

     char *r=my_strstr(dest,src);
     printf("%s\n",r);
     printf("%d\n",r-dest+1);  ///返回索引位置
     return 0;
 }
#endif // 1

#if 0  ///strlen字串長度統計函式實現
int my_strlen(const char *str)
{
    assert(NULL != str);
    char *temp = str;
    for(; *temp != '\0'; temp++);

    return (int)(temp - str);
}
int main()
{
     const char dest[]="abcefg";
     int num=my_strlen(dest);
     printf("%d\n",num);
     return 0;
 }
#endif // 1

#if 0    ///memcpy字串copy函式實現
char *my_memcpy(char * dest, const char *src, size_t count)
{
    ///char *temp_dest = (char *)dest;
    ///char *temp_src = (char *)src;
    //assert(dest != NULL && src != NULL);
    ///assert(dest>=src+count||src>dest+count);//考慮記憶體重疊的情況
    ///while(count--)
        ///*temp_dest++ = *temp_src++;

    int wordnum = count/4;//計算有多少個32位，按4位元組拷貝
    int slice = count%4;//剩餘的按位元組拷貝
    printf("wordnum=%d,slice=%d\n",wordnum,slice);
    int * pintsrc = (int *)src;
    int * pintdst = (int *)dest;
    while(wordnum--)*pintdst++ = *pintsrc++;
    char *pTempDst = (char *)pintdst;
    char *pTempSrc = (char *)pintsrc;
    printf("wordnum=%d,  slice=%d\n",wordnum,slice);
    while(slice--)
    {
        *pTempDst++ = *pTempSrc++;
    }

    return dest;
}
int main()
{
     char dest[20]="abcefg";
     const char src[]="opqrstxyz";
     printf("%d\n",sizeof(src));
     char *r=my_memcpy(dest, src, sizeof(src)-1);
     printf("%s\n",r);
     return 0;
 }
#endif // 1

#if 0  ///strcmp字串比較函式實現
int my_strcmp(const char *str1, const char *str2)
{
    int ret = 0;
    assert(str1 != NULL && str2 != NULL);

    ///法1:減法
    //while(!(ret = *(unsigned char*)str1 - *(unsigned char*)str2)&&*str1&&*str2)
    //{
        //str1++;
        //str2++;
    //}
    ///法2：==法
  /* while(*str1 == *str2 && *str1 != '\0'&&*str2) {
         str1++;
         str2++;
    }
    ret= *str1 - *str2;*/

     if(ret < 0)
        ret = -1;
    else if(ret > 0)
        ret = 1;
    return ret;
}
int main()
{
     const char dest[]="abcefg";
     const char src[]="abqrstxyz";
     int result=my_strcmp(dest, src);
     printf("%d\n",result);
     return 0;
 }
#endif // 1

#if 0  //輸出具有指定位置匹配的字串的句子
#define MAXSIZE 100
int getline(char line[],int max);
int strindex(char src[],char searchfor[]);
char pattern[]="ould";

int main()
{
    char line[MAXSIZE];
    int found=0;
    while(getline(line,MAXSIZE))
    if(strindex(line,pattern)>=0){
        printf("%s ",line);
        int num=strindex(line,pattern);
        printf("%d \n",num);
        found++;
    }
    return found;
}
int getline(char s[],int lim)
{
    int c,i;
    i=0;
    while(--lim>0 && (c=getchar())!=EOF && c!='\n')
        s[i++]=c;
    if(c=='\n')
        s[i++]=c;
    s[i]='\0';
    return i;
}
int strindex(char s[],char t[])
{
    int i,j,k;
    ///左側位置
    for(i=0;s[i]!='\0';i++){
       for(j=i,k=0;s[j]==t[k];j++,k++)
        ;
         if(j>0 && t[k]=='\0')
            return i;
    }
    /*char *bp=s;
    int sum=0,ln=strlen(t);
    while(bp=strstr(bp,t)){
        sum++;
        bp +=ln;
    }
    printf("num=%d\n",sum);
    return  (bp-s+1);*/
    ///右側位置
    /*for (i = strlen(s) - 1; i >= 0; i--)
    {
        for (j = i, k = strlen(t) - 1; k >= 0 && s[j] == t[k]; j--, k--)
            ;
        if (k  < 0)
            return j+1;
    }*/
    return -1;
}
#endif // 1