常见递归&非递归实现

void my_strcpy(char *to,const char *from)
{
    if('\0' == *from){
        *to = '\0';
        return ;
    }
    *to++ = *from++;
    my_strcpy(to,from);
}
//只拷贝n个字符
void my_strncpy(char *to,const char* from,int n)
{
    if( 0 == n || '\0' == *from){
        *to = '\0';
        return ;
    }
    *to++ = *from++;
    my_strncpy(to,from,n-1);
}
//字符串比较
int my_strcmp(const char *src,const char *dest)
{
    if((NULL == src || NULL == dest))
        return err;
    if('\0'==*src && '\0'== *dest)
        return 0;
    if(*src != *dest)
        return ( ((*src - *dest)>0)? 1 : -1 );
    my_strcmp(++src,++dest);

}
//之比较n个字符
int my_strncmp(const char* src,const char *dest,int n)
{
    if((NULL == src || NULL == dest))
        return err;
    if(0 == n)
        return 0;
    if(*src != *dest)
        return ( ((*src-*dest)>0)? 1 : -1 );
    my_strncmp(++src,++dest,--n);
}
//过滤掉重复的字符
void word_filter(char *src)
{
    if(*src == '\0')
    {
        printf("\n");
        return ;
    }
    int index = *src;
    if(tmp[index] == 0){
        tmp[index]++;
        printf("%c",*src);
    }
    word_filter(++src);
}

//字符包含问题(小写字符)
int str_include(const char *s1,const char *s2)
{
    if(NULL == s1 || NULL == s2 )
        return err;
    enum ret no=n;
    enum ret yes=y;
    unsigned int bit_map = 0x0;
    for( ; *s2 ; s2++)
        bit_map |= 0x1 << (*s2 - 'a');
    for( ; *s1 ; s1++)
        if(bit_map != (bit_map |= (0x1<<(*s1 - 'a'))))
           return no;
    return yes;
}
//找数组中的最大值
int find_max_value(int *arr,int num)
{
    if(1==num)
        return arr[0];
    int max = find_max_value(arr+1,num-1);
    if(max<arr[0])
        max=arr[0];
    return max;
}
//字符串转置
void str_nizhi(char *str,int start,int end)
{
    if(start>=end)
        return ;
    char ch=*(str+start);
    *(str+start) = *(str+end);
    *(str+end) = ch;
    str_nizhi(str,start+1,end-1);
}
//利用循环求字符串的长度
int fun_strlen(const char *src)
{
    int len=0;
    for( ; *src++; len++);
    return len;
}

//递归实现字符串的长度统计
int ret_str_len(const char *src)
{
    if(*src=='\0')
        return 0;
    return (ret_str_len(++src)+1);
}
//统计ch 中1的个数
int ch_tell(unsigned char ch)
{
    if(ch)
    {
        if(ch&0x01)
            return (ch_tell(ch>>1)+1);
        else
            return ch_tell(ch>>1);
    }
    else
        return 0;
}
//如ch :0x00 到 0xff (0~255)中有多少偶数个1(00000000:0个1、00001001:2个1)的数
int fun_tell(void)
{
    unsigned char ch = 0x0;
    int sum = 0;
    for( ; ; )
    {
        if(ch_tell(ch)%2 == 0)
            sum++;
        if(ch == 0xff)
            break ;
        ch = ch+1;
    }
    return sum;
}
//找数组中相同的值(数值不能大于数组的大小)
#if 1
int get_same_value1(int *arr,int len)
{
    if(NULL == arr || len<=0)
        return err;
    int i=0, *new_array =(int *)malloc(sizeof(int)*len);
    if(new_array == NULL)
        return err;
    //memset(new_array,-1,len);
    for( ; i<len; i++)
        new_array[i]=-1;
    for( i=0 ; i<len ; i++)
    {
        if(new_array[arr[i]] == -1)
            new_array[arr[i]] = arr[i];
        else
            return arr[i];
    }
    free(new_array);
    return 0;
}
#endif

int get_sum(int a, int b)
{
    if(b == 0)
        return a;
    int aa = a^b;
    int bb = (a&b)<<1;
    return get_sum(aa,bb);
}

void zhe_ban_insert_sort(int *arr,int len)
{
    if(NULL == arr || len<=0)
        return ;
    int tmp = 0;
    int i = 0,start=0,end=0,middle=0,j=0;
    for(i=1 ; i<len ; i++)
    {
        tmp = arr[i];
        start = 0;
        end = i-1;
        while(start<=end)
        {
            middle = (start+end)/2;
            if(arr[middle]>arr[i])
                end = middle-1;
            else
                start=middle+1;
        }
        for(j=i-1; j>=start; j--)
            arr[j+1]=arr[j];
        arr[start]=tmp;
    }
}
static inline void get_size(void)
{
    char str[] = "hello";
    char *pt = str ;
    char *ptr= NULL;
    void *p = malloc(100);
    int i =10;
    printf("sizeof str is %d\nstrlen of str is %d\n",sizeof(str),fun_strlen(str));//6,5
    printf("sizeof pt is %d\nstrlen of pt is %d\n",sizeof(pt),fun_strlen(pt));//4,5
    printf("sizeof ptr is %d\n",sizeof(ptr));//4
    printf("sizeof p is %d\n",sizeof(p));//4
    printf("sizeof i is %d\n",sizeof(i));//4
    return ;
}
void *str_str(const char *s1,const char *s2,int (*ncmp)(const char *,const char *,int))
{
    if(NULL == s2 || s2 == NULL)
        return NULL;
    int len1 = ret_str_len(s1);
    int len2 = ret_str_len(s2);
    if(len1<len2)
        return NULL;
    int i = 0;
    for( ; i<len1&&(len1-i>=len2) ; i++){
        if(!ncmp(s1+i,s2,len2))
            return s1+i;
    }
    return NULL;
}