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| #include <bits/stdc++.h>
class String {
public:
String(const char *str = nullptr);
String(const String &other);
String(String &&other);
~String();
String &operator=(const String &other);
String &operator=(String &&other);
private:
char *m_data;
};
String::String(const char *str) {
if (str == nullptr) {
m_data = new char[1];
*m_data = '\0';
} else {
int length = strlen(str);
m_data = new char[length + 1];
strcpy(m_data, str);
}
}
String::String(const String &other) {
int length = strlen(other.m_data);
m_data = new char[length + 1];
strcpy(m_data, other.m_data);
}
String::String(String &&other) {
m_data = other.m_data;
other.m_data = nullptr;
}
String::~String() {
delete[] m_data;
}
String &String::operator=(const String &other) {
if (this != &other) {
delete[] m_data;
int length = strlen(other.m_data);
m_data = new char[length + 1];
strcpy(m_data, other.m_data);
}
return *this;
}
String &String::operator=(String &&other) {
if (this != &other) {
delete[] m_data;
m_data = other.m_data;
other.m_data = nullptr;
}
return *this;
}
int main() {
String s1;
String s2("Hello");
String s3(s2);
String s4(std::move(s3));
String s5;
s5 = s4;
String s6;
s6 = std::move(s5);
system("pause");
return 0;
}
|
strlen和sizeof的区别
int length = strlen(str); 计算了 str 指向的字符串的长度，并将结果存储在 length 变量中。
sizeof 获取的是指针的大小
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| #include <bits/stdc++.h>
class String {
public:
String(const char *str = nullptr);
String(const String &other);
String(String &&other);
~String();
String &operator=(const String &other);
String &operator=(String &&other);
public:
char *m_data;
int m_length;
};
String::String(const char *str) {
if (str == nullptr) {
m_data = nullptr;
m_length = 0;
} else {
int length = strlen(str);
m_data = new char[length];
strcpy(m_data, str);
m_length = length;
}
}
String::String(const String &other) {
int length = strlen(other.m_data);
m_data = new char[length];
strcpy(m_data, other.m_data);
m_length = length;
}
String::String(String &&other) {
m_data = other.m_data;
m_length = other.m_length;
other.m_data = nullptr;
}
String::~String() {
delete[] m_data;
}
String &String::operator=(const String &other) {
if (this != &other) {
delete[] m_data;
int length = strlen(other.m_data);
m_data = new char[length];
strcpy(m_data, other.m_data);
m_length = length;
}
return *this;
}
String &String::operator=(String &&other) {
if (this != &other) {
delete[] m_data;
m_data = other.m_data;
other.m_data = nullptr;
m_length = other.m_length;
}
return *this;
}
int main() {
String s1;
String s2("Hello");
for (int i = 0; i < s2.m_length; i++) {
std::cout << s2.m_data[i];
}
std::cout << std::endl;
String s3(s2);
String s4(std::move(s3));
String s5;
s5 = s4;
String s6;
s6 = std::move(s5);
system("pause");
return 0;
}
|
