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串第一次听说，实际上就和C++封装好的string对象类似。本例题中，利用C++自实现了string类的一些功能函数，一方面回顾c++的一些知识，另一方面也加深对string对象的了解。编程过程中，为了省事，也或多或少利用了string的函数，例如size()，clear()等。

Stringv1() {
    length = 0; }   //构造函数Stringv1(const Stringv1 & s);   //复制构造函数Stringv1(const char *c);   //将c风格字符串转string对象Stringv1 &operator=(const Stringv1 & s);   //赋值函数void Show() const;   //展示对象信息bool ClearString();   //清除对象bool isEmpty() const {
    return (length == 0); }  //判断串是否为空int Length() const {
    return length; }   //返回串的长度string SubString(int pos, int len);   //返回从pos开始的后len长度的串int Index(const string & s, const int pos);   //查找pos之后的第一个与s相同的子串int Replace(const string & s1, const string & s2);   //用s2替换掉串中的s1string StrInsert(const string & s1, int pos);   //在串的pos之后插入子串s1//这里用到了两个友元函数，目的是为了加强练习，也可以用类的公有函数代替friend int StrCompare(const Stringv1 & s1, const Stringv1 & s2);//比较两个串是否相同friend Stringv1 Concat(const Stringv1 & s1, const Stringv1 & s2);//将两个串连接在一起

示例输出结果：

This is a char array!has 21 charater.This is a char array!has 21 charater.String is cleared!The two string is equal!Substring:is a charFind the first substring "is" at 2Using "at" replace isAfter 2 time replace, the string is: That at a char array!has 21 charater.After insert a string:That insert at a char array!

串的基本功能实现头文件：

#pragma once#ifndef STRINGV1_H_#define STRINGV1_H_#include
   
    #include
    
     using namespace std;class Stringv1{
   private:	string data;	int length;public:	Stringv1() {
    length = 0; }	Stringv1(const Stringv1 & s);	Stringv1(const char *c);	Stringv1 &operator=(const Stringv1 & s);	void Show() const;	bool ClearString();	bool isEmpty() const {
    return (length == 0); }	int Length() const {
    return length; }	string SubString(int pos, int len);	int Index(const string & s, const int pos);	int Replace(const string & s1, const string & s2);	string StrInsert(const string & s1, int pos);	friend int StrCompare(const Stringv1 & s1, const Stringv1 & s2);	friend Stringv1 Concat(const Stringv1 & s1, const Stringv1 & s2);};Stringv1::Stringv1(const Stringv1 & s){
   	data = s.data;	length = s.length;}Stringv1::Stringv1(const char *c){
   	length = strlen(c);	for (int i = 0; i < length; i++)		data.push_back(c[i]);}Stringv1 &Stringv1::operator=(const Stringv1 & s){
   	data = s.data;	length = s.length;	return *this;}void Stringv1::Show() const{
   	cout << data << endl;	cout << "has " << length << " charater.\n";}bool Stringv1::ClearString(){
   	length = 0;	data.clear();	return true;}int StrCompare(const Stringv1 & s1, const Stringv1 & s2){
   	if (s1.data.size() == 0 || s2.data.size() == 0) {
   		cout << "Least an object is null.\n";		exit(EXIT_FAILURE);	}	else {
   		int i = 0;		while (i
     
      
        length) {
   		cout << "The substring is too long!\n";		exit(EXIT_FAILURE);	}	else		for (int i = 0; i < len; i++)			out.push_back(data[pos + i]);	return out;}int Stringv1::Index(const string & s, const int pos){
   	if (s.empty()) {
   		cout << "is empty!\n";		return 0;	}	for (int i = pos; i < length; i++) {
   		int j = 0;		while (j < s.size() && i < length&&s[j] != data[i])			i++;		int temp = i;		while (j < s.size() && i < length&&s[j] == data[i]) {
   			i++; j++;		}		if (j == s.size())			return temp;		else			i = temp + 1;	}	return 0;}int Stringv1::Replace(const string & s1, const string & s2){
   	if (s1.size() != s2.size()) {
   		cout << "Must have same length!\n";		return 0;	}	int time = 0;	for (int i = 0; i < length; ) {
   		int  index = Index(s1, i);		if (index) {
   			for (char temp : s2) {
   				data[index] = temp;				index++;			}			time++;			i = index + 1;		}		else if (index == 0)			return time;	}}string Stringv1::StrInsert(const string & s1, int pos){
   	if (s1.size() == 0)		cout << "The string is empty!\n";	if (pos > length)		cout << "The index is out of range!\n";	return this->SubString(0, pos - 1) + s1 +		this->SubString(pos - 1, length - pos + 1);}#endif // !STRINGV1_H_
      
     
    
   

串的基本功能示例：

#include
   
    #include
    
     #include"stringv1.h"using namespace std;void main(){
   	char test1[] = "This is a char array!";	Stringv1 test2(test1);	test2.Show();	Stringv1 test3;	test3 = test2;	test3.Show();	if (test3.ClearString())		cout << "String is cleared!\n";	if (!StrCompare(test1, test2))		cout << "The two string is equal!\n";	cout << "Substring: \n";	cout << test2.SubString(5, 10) << endl;	string s1 = "is";	cout << "Find the first substring \"" << s1 << "\" at ";	cout << test2.Index(s1, 1) << endl;	string s2 = "at";	cout << "Using \"" << s2 << "\" replace " << s1 << endl;	int time = test2.Replace(s1, s2);	cout << "After " << time << " time replace, the string is: ";	test2.Show();	string s3 = "insert ";	cout << "After insert a string: \n";	cout << test2.StrInsert(s3, 6) << endl;}
    
   

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