CString &csVar(cslistTagName.GetNext(nPos)); 和 CString csVar(cslistTagName.GetNext(nPos)); 区别

`CString &csVar(cslistTagName.GetNext(nPos))` 是将 `cslistTagName.GetNext(nPos)` 的返回值作为引用传递给 `csVar`，也就是说，`csVar` 引用了 `cslistTagName` 中下一个元素的值，同时也会影响到 `cslistTagName` 中对应元素的值。在使用引用传递时，修改 `csVar` 的值也会修改 `cslistTagName` 对应元素的值。

而 `CString csVar(cslistTagName.GetNext(nPos))` 则是将 `cslistTagName.GetNext(nPos)` 的返回值拷贝一份到 `csVar` 中，这样就不会影响到 `cslistTagName` 中对应元素的值。在这种情况下，修改 `csVar` 的值也不会修改 `cslistTagName` 对应元素的值。

因此，如果需要对 `cslistTagName` 中的元素进行修改，可以使用第一种方式，否则可以使用第二种方式。

相关问题

#include <iostream> #include <cstring> using namespace std; class CSTRING { public: CSTRING() : ptr(nullptr), len(0) {} CSTRING(const char* str) { len = strlen(str); ptr = new char[len + 1]; strcpy(ptr, str); } CSTRING(const CSTRING& other) { len = other.len; ptr = new char[len + 1]; strcpy(ptr, other.ptr); } ~CSTRING() { if (ptr != nullptr) { delete[] ptr; ptr = nullptr; } } CSTRING& operator=(const CSTRING& rhs) { if (this != &rhs) { if (ptr != nullptr) { delete[] ptr; } len = rhs.len; ptr = new char[len + 1]; strcpy(ptr, rhs.ptr); } return *this; } CSTRING operator+(const CSTRING& rhs) const { CSTRING result; result.len = len + rhs.len; result.ptr = new char[result.len + 1]; strcpy(result.ptr, ptr); strcat(result.ptr, rhs.ptr); return result; } CSTRING& operator+=(const CSTRING& rhs) { len += rhs.len; char* temp = new char[len + 1]; strcpy(temp, ptr); strcat(temp, rhs.ptr); delete[] ptr; ptr = temp; return *this; } char& operator[](int index) { return ptr[index]; } void insert(const char* str, int pos) { int str_len = strlen(str); char* temp = new char[len + str_len + 1]; strncpy(temp, ptr, pos); strcpy(temp + pos, str); strcpy(temp + pos + str_len, ptr + pos); delete[] ptr; ptr = temp; len += str_len; } bool operator>(const CSTRING& rhs) const { return strcmp(ptr, rhs.ptr) > 0; } friend ostream& operator<<(ostream& os, const CSTRING& str); friend istream& operator>>(istream& in, const CSTRING& str); private: char* ptr; int len; }; ostream& operator<<(ostream& os, const CSTRING& str) { os <<"--"<<str.ptr; return os; } istream& operator>>(istream& in, const CSTRING& str) { for (int i = 0; i < str.len ; i++) { cin>>str.ptr[i]; } return in; } int main() { int n, i, j; while (cin >> n) { CSTRING *c = new CSTRING[n + 2]; for (i = 0; i < n; i++) { cin >> c[i]; } for (i = 0; i < n - 1; i++) for (j = 0; j < n - i - 1; j++) if (c[j] > c[j + 1]) { c[n] = c[j]; c[j] = c[j + 1]; c[j + 1] = c[n]; } for (i = 0; i < n; i++) c[n + 1] += c[i]; cout << c[n + 1] << endl; delete[] c; } return 0; }帮我调整代码使其能输出--aaa--bbb--ccc

好的，以下是已修改的代码，可以输出--aaa--bbb--ccc：

#include <iostream>
#include <cstring>
using namespace std;

class CSTRING {
public:
    CSTRING() : ptr(nullptr), len(0) {}
    CSTRING(const char* str) {
        len = strlen(str);
        ptr = new char[len + 1];
        strcpy(ptr, str);
    }
    CSTRING(const CSTRING& other) {
        len = other.len;
        ptr = new char[len + 1];
        strcpy(ptr, other.ptr);
    }
    ~CSTRING() {
        if (ptr != nullptr) {
            delete[] ptr;
            ptr = nullptr;
        }
    }

    CSTRING& operator=(const CSTRING& rhs) {
        if (this != &rhs) {
            if (ptr != nullptr) {
                delete[] ptr;
            }
            len = rhs.len;
            ptr = new char[len + 1];
            strcpy(ptr, rhs.ptr);
        }
        return *this;
    }

    CSTRING operator+(const CSTRING& rhs) const {
        CSTRING result;
        result.len = len + rhs.len;
        result.ptr = new char[result.len + 1];
        strcpy(result.ptr, ptr);
        strcat(result.ptr, rhs.ptr);
        return result;
    }

    CSTRING& operator+=(const CSTRING& rhs) {
        len += rhs.len;
        char* temp = new char[len + 1];
        strcpy(temp, ptr);
        strcat(temp, rhs.ptr);
        delete[] ptr;
        ptr = temp;
        return *this;
    }

    char& operator[](int index) {
        return ptr[index];
    }


    void insert(const char* str, int pos) {
        int str_len = strlen(str);
        char* temp = new char[len + str_len + 1];
        strncpy(temp, ptr, pos);
        strcpy(temp + pos, str);
        strcpy(temp + pos + str_len, ptr + pos);
        delete[] ptr;
        ptr = temp;
        len += str_len;
    }

    bool operator>(const CSTRING& rhs) const {
        return strcmp(ptr, rhs.ptr) > 0;
    }

    friend ostream& operator<<(ostream& os, const CSTRING& str);
    friend istream& operator>>(istream& in, CSTRING& str);

private:
    char* ptr;
    int len;
};

ostream& operator<<(ostream& os, const CSTRING& str) {
    os << "--" << str.ptr << "--";
    return os;
}

istream& operator>>(istream& in, CSTRING& str) {
    in >> str.ptr;
    return in;
}

int main() {
    int n, i, j;
    while (cin >> n) {
        CSTRING* c = new CSTRING[n + 2];
        for (i = 0; i < n; i++) {
            cin >> c[i];
        }
        for (i = 0; i < n - 1; i++)
            for (j = 0; j < n - i - 1; j++)
                if (c[j] > c[j + 1]) {
                    c[n] = c[j];
                    c[j] = c[j + 1];
                    c[j + 1] = c[n];
                }
        for (i = 0; i < n; i++)
            c[n + 1] += c[i];
        cout << c[n + 1] << endl;
        delete[] c;
    }
    return 0;
}

主要的修改在于`operator<<`和`operator>>`的实现。其中`operator<<`在输出字符串前后添加了"--"，而`operator>>`直接对`ptr`进行了输入，不需要循环输入每个字符。

将此文件改为多文件#include<iostream> #include<string.h> using namespace std; class CSTRING { private: char* p; public: CSTRING() { int len = 0; p = new char[len + 1]; p[0] = '\0'; } CSTRING(const char* str) { int len = strlen(str); p = new char[len + 1]; strcpy(p, str); } CSTRING(const CSTRING& str) { int len = strlen(str.p); p = new char[len + 1]; strcpy(p, str.p); } CSTRING operator+=( CSTRING& s) { char* str = new char[strlen(p) + strlen(s.p) + 3]; str[0] = '\0'; strcat(str, p); strcat(str, "--"); strcat(str, s.p); delete[]p; p = str; return *this; } friend ostream& operator<<(ostream& out, CSTRING& str); friend istream& operator>>(istream& in, CSTRING& str); int operator>(const CSTRING& str); }; ostream& operator<<(ostream& out, CSTRING& str) { out << str.p; return out; } istream& operator>>(istream& in, CSTRING& str) { in >> str.p; return in; } int CSTRING:: operator>(const CSTRING& str) { if (strcmp(p, str.p)>0){ return 1; }else {return 0; } } int main() { int n, i, j; while (cin >> n) { CSTRING *c = new CSTRING[n + 2]; for (i = 0; i < n; i++) { cin >> c[i]; } for (i = 0; i < n - 1; i++) for (j = 0; j < n - i - 1; j++) if (c[j] > c[j + 1]) { c[n] = c[j]; c[j] = c[j + 1]; c[j + 1] = c[n]; } for (i = 0; i < n; i++) c[n + 1] += c[i]; cout << c[n + 1] << endl; delete[] c; } return 0; }

这里提供一个多文件的实现，将CSTRING类的定义和实现分别放在CSTRING.h和CSTRING.cpp文件中，主函数放在main.cpp文件中。

CSTRING.h文件内容如下：

#ifndef CSTRING_H
#define CSTRING_H

#include<iostream>
#include<string.h>

using namespace std;

class CSTRING {
private:
    char* p;

public:
    CSTRING();
    CSTRING(const char* str);
    CSTRING(const CSTRING& str);
    ~CSTRING();

    CSTRING operator+=(CSTRING& s);
    int operator>(const CSTRING& str);

    friend ostream& operator<<(ostream& out, CSTRING& str);
    friend istream& operator>>(istream& in, CSTRING& str);
};

#endif

CSTRING.cpp文件内容如下：

#include "CSTRING.h"

CSTRING::CSTRING() {
    int len = 0;
    p = new char[len + 1];
    p[0] = '\0';
}

CSTRING::CSTRING(const char* str) {
    int len = strlen(str);
    p = new char[len + 1];
    strcpy(p, str);
}

CSTRING::CSTRING(const CSTRING& str) {
    int len = strlen(str.p);
    p = new char[len + 1];
    strcpy(p, str.p);
}

CSTRING::~CSTRING() {
    delete[] p;
}

CSTRING CSTRING::operator+=(CSTRING& s) {
    char* str = new char[strlen(p) + strlen(s.p) + 3];
    str[0] = '\0';
    strcat(str, p);
    strcat(str, "--");
    strcat(str, s.p);
    delete[]p;
    p = str;
    return *this;
}

int CSTRING::operator>(const CSTRING& str) {
    if (strcmp(p, str.p) > 0) {
        return 1;
    }
    else {
        return 0;
    }
}

ostream& operator<<(ostream& out, CSTRING& str) {
    out << str.p;
    return out;
}

istream& operator>>(istream& in, CSTRING& str) {
    in >> str.p;
    return in;
}

main.cpp文件内容如下：

#include<iostream>
#include"CSTRING.h"

using namespace std;

int main() {
    int n, i, j;
    while (cin >> n)
    {
        CSTRING* c = new CSTRING[n + 2];
        for (i = 0; i < n; i++)
        {
            cin >> c[i];
        }
        for (i = 0; i < n - 1; i++)
            for (j = 0; j < n - i - 1; j++)
                if (c[j] > c[j + 1])
                {
                    c[n] = c[j];
                    c[j] = c[j + 1];
                    c[j + 1] = c[n];
                }
        for (i = 0; i < n; i++)
            c[n + 1] += c[i];
        cout << c[n + 1] << endl;
        delete[] c;
    }
    return 0;
}