使用C++的朋友对string类都不会陌生,string类使用起来很是方便,比C的字符数组好用多了,但是我们能不能自己实现一个属于自己的string类呢?
实现一个具有基本功能的string类并不难,但是还是得掌握以下几点知识:构造函数、析构函数、运算符重载、指针、引用等等。
我自己实现了一个string类,一来是想用自己学的知识做一些有实际作用的东西,二则使用自己的东西也很有成就感,现在给大家作为参考,有错误或者不合理的地方欢迎大家指正。
为了区别标准库中的string类和相关标识符,我的类名叫mystring,而相关函数名也大多以这种方式处理,其中每个函数都经过本人测试,在参数合法的前提下均能正常使用,但组合在一起使用的情况则没有进行太多测试。
首先是mystring.h文件
#ifndef MYSTRING_H_INCLUDED #define MYSTRING_H_INCLUDED #include <iostream> using namespace std; class mystring { public: mystring(); mystring(const char * ptr_s); mystring(const mystring & refer_str);//拷贝构造函数 int mylength();//计算字符串的长度 ~mystring(); friend istream & operator>>(istream & is, mystring & refer_str); friend ostream & operator<<(ostream & os, const mystring & refer_str); mystring & operator=(const mystring & refer_str); void mygetline();//对输入按行读取 char & operator[](int n); friend mystring operator+(const mystring & refer_str_1, const mystring & refer_str_2); mystring & operator+=(const mystring & refer_str); friend bool operator==(const mystring & refer_str_1, const mystring & refer_str_2); friend bool operator!=(const mystring & refer_str_1, const mystring & refer_str_2); mystring mysubstr(int pos, int posn);//计算一个字符串的子串,pos为起始位置,从0开始,posn为希望求得的子串的长度 friend void mystrswap(mystring & str1, mystring & str2);//交换两个字符串 int myfind(char ch, int pos = 0);//从pos开始查找字符ch在当前字符串中的位置,pos从0开始,返回值也从0开始 mystring & myerase(int pos, int posn);//从pos开始删除当前字符串中的字符,pos从0开始,posn表示希望删除的字符数量,返回删除后字符串的引用,也即当前字符串 mystring & myinsert(int pos, const mystring & refer_str);//将refer_str代表的字符串插入到当前字符串中,pos表示插入的位置,0 <= pos <= mystrlen((*this).ptr_s) mystring & myinsert(int pos, const mystring & refer_str, int posn);//将refer_str代表的字符串插入到当前字符串中,pos表示插入的位置,0 <= pos <= mystrlen((*this).ptr_s),0 <= posn <= mystrlen(refer_str.ptr_s) private: char * ptr_s; }; int mystrlen(const char * ptr_s);//计算字符串的长度 void mystrcpy(char * ptr_s_1, const char * ptr_s_2);//将ptr_s_2指向的内容复制到ptr_s_1所指向的空间,但前提后者空间足够 int mystrcmp(const char * ptr_s_1, const char * ptr_s_2);//比较ptr_s_1指向的内容和ptr_s_2指向的内容,若两者相同返回0,前者大返回1,前者小返回-1 void mystrcat(char * ptr_s_1, const char * ptr_s_2);//将ptr_s_2指向的内容连接到ptr_s_1指向的内容的后面,但需保证ptr_s_1所指向的空间足够,并且ptr_s_1所指向的空间必须经过初始化,即包含有意义的字符串结束符\0 #endif // MYSTRING_H_INCLUDED
我的想法是尽量不使用标准库,但为了重载>>和<<这两个运算符并实现mygetline()函数,还是得在mystring.h中包含iostream。
然后是mystring.cpp文件
#include "mystring.h" mystring::mystring() { ptr_s = new char[1]; *ptr_s = ‘\0‘; } mystring::mystring(const char * ptr_s) { this->ptr_s = new char[mystrlen(ptr_s)+1]; mystrcpy(this->ptr_s, ptr_s); } mystring::mystring(const mystring & refer_str) { ptr_s = new char[mystrlen(refer_str.ptr_s)+1]; mystrcpy(ptr_s, refer_str.ptr_s); } int mystring::mylength() { return mystrlen(ptr_s); } mystring::~mystring() { delete [] ptr_s; } istream & operator>>(istream & is, mystring & refer_str) { delete [] refer_str.ptr_s; char ch_tmp[1000];// 申请一块在一般情况下足够大的内存 is >> ch_tmp; refer_str.ptr_s = new char[mystrlen(ch_tmp)+1]; mystrcpy(refer_str.ptr_s, ch_tmp); return is; } ostream & operator<<(ostream & os, const mystring & refer_str) { os << refer_str.ptr_s; return os; } mystring & mystring::operator=(const mystring & refer_str) { if(this == &refer_str) return *this; else { delete [] ptr_s; ptr_s = new char[mystrlen(refer_str.ptr_s)+1]; mystrcpy(ptr_s, refer_str.ptr_s); return *this; } } void mystring::mygetline() { delete [] ptr_s; char ch_tmp[1000];// 申请一块在一般情况下足够大的内存 cin.getline(ch_tmp, 1000); ptr_s = new char[mystrlen(ch_tmp)+1]; mystrcpy(ptr_s, ch_tmp); } char & mystring::operator[](int n) { return *(ptr_s+n); } mystring operator+(const mystring & refer_str_1, const mystring & refer_str_2) { mystring str_tmp; str_tmp.ptr_s = new char[mystrlen(refer_str_1.ptr_s)+mystrlen(refer_str_2.ptr_s)+1]; mystrcpy(str_tmp.ptr_s, refer_str_1.ptr_s); mystrcpy(str_tmp.ptr_s+mystrlen(refer_str_1.ptr_s), refer_str_2.ptr_s); return str_tmp; } mystring & mystring::operator+=(const mystring & refer_str) { mystring str_tmp; str_tmp.ptr_s = new char[mystrlen(ptr_s)+mystrlen(refer_str.ptr_s)+1]; mystrcpy(str_tmp.ptr_s, ptr_s); mystrcpy(str_tmp.ptr_s+mystrlen(ptr_s), refer_str.ptr_s); delete [] ptr_s; ptr_s = new char[mystrlen(str_tmp.ptr_s)+1]; mystrcpy(ptr_s, str_tmp.ptr_s); return *this; } bool operator==(const mystring & refer_str_1, const mystring & refer_str_2) { int ret = mystrcmp(refer_str_1.ptr_s, refer_str_2.ptr_s); if(ret == 0) return true; else return false; } bool operator!=(const mystring & refer_str_1, const mystring & refer_str_2) { int ret = mystrcmp(refer_str_1.ptr_s, refer_str_2.ptr_s); if(ret == 0) return false; else return true; } mystring mystring::mysubstr(int pos, int posn) { mystring str_tmp; delete [] str_tmp.ptr_s; str_tmp.ptr_s = new char[posn+1]; for(int i = 0;i < posn;i++) *(str_tmp.ptr_s+i) = *(ptr_s+pos+i); *(str_tmp.ptr_s+posn) = ‘\0‘; return str_tmp; } void mystrswap(mystring & str1, mystring & str2) { char * ptr_s; ptr_s = str1.ptr_s; str1.ptr_s = str2.ptr_s; str2.ptr_s = ptr_s; } int mystring::myfind(char ch, int pos) { int str_length = mystrlen(ptr_s); int i; for(i = 0;i < str_length-pos;i++) if(*(ptr_s+pos+i) == ch) return pos+i; return -1; } mystring & mystring::myerase(int pos, int posn) { mystring str_tmp; delete [] str_tmp.ptr_s; int str_length = mystrlen(ptr_s); str_tmp.ptr_s = new char[str_length-posn+1]; for(int i = 0;i < pos;i++) *(str_tmp.ptr_s+i) = *(ptr_s+i); for(int i = pos+posn;i < str_length;i++) *(str_tmp.ptr_s+i-posn) = *(ptr_s+i); *(str_tmp.ptr_s+str_length-posn) = ‘\0‘; char * ptr_s_tmp; ptr_s_tmp = str_tmp.ptr_s; str_tmp.ptr_s = ptr_s; ptr_s = ptr_s_tmp; return *this; } mystring & mystring::myinsert(int pos, const mystring & refer_str) { mystring str_tmp; delete [] str_tmp.ptr_s; int str_length_1 = mystrlen(ptr_s); int str_length_2 = mystrlen(refer_str.ptr_s); str_tmp.ptr_s = new char[str_length_1+str_length_2+1]; int i; for(i = 0;i < pos;i++) *(str_tmp.ptr_s+i) = *(ptr_s+i); mystrcpy(str_tmp.ptr_s+i, refer_str.ptr_s); while(i < str_length_1) { *(str_tmp.ptr_s+str_length_2+i) = *(ptr_s+i); i++; } *(str_tmp.ptr_s+str_length_1+str_length_2) = ‘\0‘; char * ptr_s_tmp; ptr_s_tmp = str_tmp.ptr_s; str_tmp.ptr_s = ptr_s; ptr_s = ptr_s_tmp; return *this; } mystring & mystring::myinsert(int pos, const mystring & refer_str, int posn) { mystring str_tmp; delete [] str_tmp.ptr_s; int str_length = mystrlen(ptr_s); str_tmp.ptr_s = new char[str_length+posn+1]; int i; for(i = 0;i < pos;i++) *(str_tmp.ptr_s+i) = *(ptr_s+i); for(int j = 0;j < posn;j++) *(str_tmp.ptr_s+pos+j) = *(refer_str.ptr_s+j); while(i < str_length) { *(str_tmp.ptr_s+posn+i) = *(ptr_s+i); i++; } *(str_tmp.ptr_s+str_length+posn) = ‘\0‘; char * ptr_s_tmp; ptr_s_tmp = str_tmp.ptr_s; str_tmp.ptr_s = ptr_s; ptr_s = ptr_s_tmp; return *this; } int mystrlen(const char * ptr_s) { int length = 0; while(*(ptr_s++) != ‘\0‘) length++; return length; } void mystrcpy(char * ptr_s_1, const char * ptr_s_2) { while(*ptr_s_2 != ‘\0‘) { *ptr_s_1 = *ptr_s_2; ptr_s_1++; ptr_s_2++; } *ptr_s_1 = ‘\0‘; } int mystrcmp(const char * ptr_s_1, const char * ptr_s_2) { int length_1 = mystrlen(ptr_s_1); int length_2 = mystrlen(ptr_s_2); int length_shorter = length_1 > length_2 ? length_2 : length_1; int i; for(i = 0;i < length_shorter;i++) if(*(ptr_s_1+i) != *(ptr_s_2+i)) break; if(i == length_shorter) { if(length_1 == length_2) return 0; else if(length_1 > length_2) return 1; else return -1; } else { if(*(ptr_s_1+i) > *(ptr_s_2+i)) return 1; else return -1; } } void mystrcat(char * ptr_s_1, const char * ptr_s_2) { ptr_s_1 += mystrlen(ptr_s_1); while(*ptr_s_2 != ‘\0‘) { *ptr_s_1 = *ptr_s_2; ptr_s_1++; ptr_s_2++; } *ptr_s_1 = ‘\0‘; }
实现时很多地方用到了指针,指针确实非常强大。
这样只要将这两个文件放在目标工程文件夹里,并且在开头加上
#include "mystring.h"
就可以使用自己的string类了,如果自己需要什么个性化的功能,还可以自由添加修改。
时间: 2024-10-08 09:47:59