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问题:
解答:
main.cpp
cpp
#include <iostream>
#include "String.h"
using namespace std;
int main()
{
String s1(" and I am a C++ student.");
String s2 = "Please enter your name: ";
String s3;
cout << s2;
cin >> s3;
s2 = "My name is " + s3;
cout << s2 << ".\n";
s2 = s2 + s1;
s2.stringup();
cout << "The string\n" << s2 << "\ncontains " << s2.has('A') << " 'A' characters in it.\n";
s1 = "red";
String rgb[3] = { String(s1),String("green"),String("blue") };
cout << "Enter the name of a primary color for mixing light: ";
String ans;
bool success = false;
while (cin >> ans)
{
ans.stringlow();
for (int i = 0; i < 3; i++)
{
if (ans == rgb[i])
{
cout << "That's right!\n";
success = true;
break;
}
}
if (success)break;
else cout << "Try again!\n";
}
cout << "Bye!" << endl;
return 0;
return 0;
}
String.h
cpp
#pragma once
#include <iostream>
using namespace std;
class String
{
private:
char* str;
int len;
static int num_strings;
static const int CINLIM = 80;
public:
String();
String(const char*s);
String(const String&s);
~String();
int lengh()const { return len; }
String& operator=(const String&s);
String& operator=(const char*s);
char& operator[](int i);
const char& operator[](int i)const;
void stringup();
void stringlow();
int has(char c);
String operator+(const String& s);
bool operator==(const String& s);
friend bool operator<(const String& st1, const String& st2);
friend bool operator>(const String& st1, const String& st2);
friend ostream& operator<<(ostream& os, const String& s);
friend istream& operator>>(istream& is, String& s);
friend String operator+(const char* c, const String& s);
static int HowMany();
};
String.cpp
cpp
#include "String.h"
#include <cctype>
int String::num_strings = 0;
int String::HowMany()
{
return num_strings;
}
String::String()
{
//str = NULL;
//len = 0;
len = 4;
str = new char[1];
str[0] = '\0';
num_strings++;
}
String::String(const char* s)
{
len = strlen(s);
str = new char[len+1];
strcpy_s(str, len+1, s);
num_strings++;
}
String::String(const String&s)
{
len = s.len;
str = new char[len + 1];
strcpy_s(str, len + 1, s.str);
num_strings++;
}
String::~String()
{
--num_strings;
delete[] str;
}
String& String::operator=(const String& s)
{
if (this == &s)return *this;
if (str)delete[] str;
len = s.len;
str = new char[len + 1];
strcpy_s(str, len + 1, s.str);
return *this;
}
String& String::operator=(const char* s)
{
if (str)delete[] str;
len = strlen(s);
str = new char[len + 1];
strcpy_s(str, len + 1, s);
return *this;
}
char& String::operator[](int i)
{
return str[i];
}
const char& String::operator[](int i)const
{
return str[i];
}
void String::stringup()
{
for (int i = 0; i < len;i++)
{
str[i] = toupper(str[i]);
}
}
void String::stringlow()
{
for (int i = 0; i < len; i++)
{
str[i] = tolower(str[i]);
}
}
int String::has(char c)
{
int count = 0;
for (int i = 0; i < len; i++)
{
if (str[i] == c)
{
count++;
}
}
return count;
}
String String::operator+(const String& s)
{
/*if (!s.str || !str)return String();
int size = strlen(s.str) + strlen(str) + 1;
char* result = new char[size];
strcpy_s(result, strlen(str) + 1, str);
strcat_s(result,size, s.str);
return String(result);*/
String result;
result.len = s.len + len;
result.str = new char[result.len + 1];
strcpy_s(result.str, result.len+1 ,str);
strcat_s(result.str, result.len + 1, s.str);
return result;
}
bool operator<(const String& st1, const String& st2)
{
return strcmp(st1.str, st2.str) < 0;
}
bool operator>(const String& st1, const String& st2)
{
return st2 < st1;
}
bool String::operator==(const String& s)
{
bool flag = false;
for (int i = 0; i < len; i++)
{
if (str[i] == s.str[i])
{
flag = true;
}
else
{
return false;
}
}
return flag;
}
ostream& operator<<(ostream& os, const String& s)
{
os << s.str;
return os;
}
//istream& operator>>(istream& is, String& s)
//{
// char* str=NULL;
// is >> str;
// s.str = new char[strlen(str) + 1];
// strcpy_s(s.str, strlen(str) + 1, str);
// return is;
//}
istream& operator>>(istream& is, String& s) {
char buffer[256]; // 使用一个临时缓冲区
//is >> buffer; // 读取输入到缓冲区
is.getline(buffer, 256);
// 释放之前的内存(如果有)
delete[] s.str;
// 分配新的内存并复制字符串
s.len = strlen(buffer);
s.str = new char[strlen(buffer) + 1];
strcpy_s(s.str, strlen(buffer) + 1, buffer); // 使用 strcpy_s 进行安全复制
/*char temp[String::CINLIM];
is.get(temp, String::CINLIM);
if (is)
{
s = temp;
}
while (is && is.get() != '\n')continue;*/
return is;
}
String operator+(const char* c, const String& s)
{
/*String temp;
int size = strlen(c) + strlen(s.str) + 1;
char* result = new char[size];
strcpy_s(result, size, c);
strcat_s(result,size, s.str);
temp.len = size;
temp.str = new char(size);
strcpy_s(temp.str, size, result);*/
String temp;
temp.len = s.len + strlen(c);
temp.str = new char[temp.len + 1];
strcpy_s(temp.str,temp.len+1, c);
strcat_s(temp.str, temp.len + 1, s.str);
return temp;
}
运行结果:
考查点:
- 静态数据成员
- 静态成员函数
- 拷贝构造
- 赋值构造
- 动态内存分配
- 析构
- []下标运算符的重载
- cctype字母大小写转换
- 字符串的赋值,拼接和比较
- 重载<<,>>
- 友元
注意:
- 有指针的数据成员类,一定要深拷贝!
2024年9月8日08:52:45