#include <iostream>
using namespace std;
//實現一個函數求字符串的長度。
int my_length(const char s)
{
    if (s == '\0')return 0;
    else
        return 1+my_length(s + 1);
}
int main()
{
    char *s = "123456";
    cout << my_length(s) << endl;
    return 0;
}

include <iostream>
include <assert.h>
using namespace std;
//實現一個求字符串的長度。
int my_length(const char s)
{
    if (s == NULL)return 0;
    int count = 0;
    while (s[++count] != '\0');
    return count;
}
int main()
{
    char s = "";
    cout << my_length(s) << endl;
    return 0;
}
include <iostream>
include <string.h>
include <assert.h>
using namespace std;
char my_strcpy(char dist,const char scour)
{
    assert(scour!=NULL);
    char p = dist;
    while (dist++ = scour++);
    return p;
}
int main()
{
    char s1 = "123";
    char s2 = new char[strlen(s1)];
    cout << my_strcpy(s2, s1) << endl;
    return 0;
}
include <iostream>
include <assert.h>
using namespace std;
//實現庫函數strcat。
char  my_strcat(char dist,char const scour)
{
    assert(dist!=NULL || scour!=NULL);
    if (scour == '\0')return dist;
    char p = dist;
    while (dist != '\0')dist++;
    while (dist++ = scour++);
    return p;
}
int main()
{
    char *s1 = new char[10];
    strcpy(s1,"123");
    cout << my_strcat(s1,"456")<<endl;
    return 0;
}
include <iostream>
include <assert.h>
include <string.h>
using namespace std;
//編寫程序使字符串逆序。
char my_invert(char s)
{
    assert(s != NULL);
    char head = s;
    char last = s+strlen(s)-1;
    char temp;
    while (head < last)
    {
        temp = head;
        head = last;
        last = temp;
        head++;
        last--;
    }
    return s;
}
int main()
{
    char *s = new char[10];
    strcpy(s,"12345");
    cout << my_invert(s) << endl;
    return 0;
}
include <iostream>
include <assert.h>
using namespace std;
//模擬實現strchr函數，功能：在一個字符串中查找一個字符第一次出現的位置，如果沒有出現返回NULL。
int my_strchar(const char dist, char ch)
{
    assert(dist!=NULL);
    int count = 0;
    while (dist != '\0' && dist!=ch)
    {
        count++;
        dist++;
    }
    if (dist == '\0')return 0;
    return count+1;
}
int main()
{
    cout << my_strchar("1234", '1') << endl;
    return 0;
}</pre>