vc++相关程序问题

vc++相关程序问题以及其面向对象程序设计初步实践相关问题……

运行结果及代码如下：

#include <iostream>
using namespace std;
class String
{
private:
    char* str;
    int len;
public:
    String(const char* ptr)
    {
        int i = 0;
        while (ptr[i] != '\0')
            i++;
        len = i;
        str = new char[len + 1];
        i = 0;
        while (ptr[i] != '\0')
        {
            str[i] = ptr[i];
            i++;
        }
        str[i] = 0;//结尾
            
    }

    char getc(int n)
    {
        if (n > 0 && n <= len)
            return str[n - 1];
        else
            return 0;
    }

    void setc(int n, char c)
    {
        if (n > 0 && n <= len)
            str[n-1] = c;
    }
    void setlen()
    {
        int i = 0;
        if (str == 0)
        {
            len = 0;
            return;
        }
        while (str[i])
            i++;
        len = i;
    }
    void show()
    {
        if (str)
            cout << str << endl;
        else
            cout << "字符串为空" << endl;
    }
    ~String()
    {
        if (str)
        {
            delete[] str;
            str = 0;
        }
    }
};

int main()
{
    char buf[100], c;
    cout << "请输入一个字符串：";
    cin >> buf;
    String s(buf);
    int n;
    cout << "获取第n个字符，请输入n：";
    cin >> n;
    cout << "第" << n << "个字符是：" << s.getc(n) << endl;
    cout << "设置第n个字符，请输入n和字符：";
    cin >> n  >> c;
    s.setc(n, c);
    cout << "字符串为：";
    s.show();
    return 0;
}

#include <iostream>
#include <string.h>
using namespace std;
class String
{
private:
char *str;
int len;
public: 
String(const char *ptr){
if (!ptr)
    {
        str = new char[1];
        *str = '\0';
    }
    else
    {
        int nLen = strlen(ptr);
        str = new char[nLen + 1];
        strcpy(str, ptr);
    }
}
~String ()
{
if(str != NULL)
free(str);
}
char getc(int n){
    return str[n];
}

void setc(int n,char c){
    str[n]=c;
}

void setlen(){
    len=strlen(str);
}

void show(){
    printf("字符串内容：%s,字符串长度：%d",str,len);
}
};
int main(){
    String sss("abcdef");
    printf("%c\n",sss.getc(2));
    sss.setc(2,'d');
    sss.setlen();
    sss.show();
    return 0;
}

您好，我是有问必答小助手，您的问题已经有小伙伴帮您解答，感谢您对有问必答的支持与关注！
PS：问答VIP年卡 【限时加赠：IT技术图书免费领】，了解详情>>> https://vip.csdn.net/askvip?utm_source=1146287632