c++实现字符串操作

// 串操作.cpp: 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include<iostream>
#include<string>
#define max 100
using namespace std;

class MyString 
{
private:
	char *str;
	int length;
public:
	MyString(const char *str_);
	~MyString();
	int getlen();															//获取字符串长度
	void insert(int position, const char *str_);							//插入字符串
	void remove(int beginposition, int endposition);						//删除字符串
	void update(int beginposition, int endposition, const char *str_);		//更新字符串
	void display();															//打印字符串
	char search(int position);												//按位置取字符
};

MyString::MyString(const char *str_)
{
	int i;
	str = new char[max];
	for (i = 0; str_[i] != '\0'; i++)
		str[i] = str_[i];
	length = i;
}

MyString::~MyString()
{
	delete[] str;
}

int MyString::getlen()
{
	return length;
}

void MyString::insert(int position, const char *str_)
{
	int str_length = MyString(str_).getlen();
	for (int i = 0; i < length - position + 1; i++)
		str[length + str_length - 1 - i] = str[length - 1 - i];			//移动																
	for (int i = 0; i < str_length; i++)
		str[position - 1 + i] = str_[i];								//插入																
	length = str_length + length;										//更新长度
}

void MyString::remove(int beginposition, int endposition)
{
	for (int i = 0; i < length - beginposition + 1; i++)
		str[beginposition - 1 + i] = str[endposition + i];				//删除
	length = length - (endposition - beginposition + 1);				//更新长度
}	

void MyString::update(int beginposition, int endposition, const char *str_)
{
	int i = 0;
	int str_length = MyString(str_).getlen();
	int len = (endposition - beginposition) + 1;
	if (len == str_length)												//分三种情况
	{																	//先移动再覆盖
		for (i = 0; i < len; i++)
			str[beginposition - 1 + i] = str_[i];
	}
	else if (len < str_length)
	{
		for (i = 0; i < length - endposition + 1; i++)
			str[length + str_length - len - 1 - i] = str[length - 1 - i];
		for (i = 0; i < str_length; i++)
			str[beginposition - 1 + i] = str_[i];
		length = length + str_length - len;
	}
	else
	{
		for (i = 0; i < length - endposition; i++)
			str[endposition - (len - str_length) + i] = str[endposition + i];
		for (i = 0; i < str_length; i++)
			str[beginposition - 1 + i] = str_[i];
		length = length + str_length - len;
	}

}

void MyString::display()
{
	for (int i = 0; i < length; i++)
		cout << str[i];
	cout << endl;
}

char MyString::search(int position)
{
	return str[position-1];
}

int main()
{
	MyString s("abcdefghijk");
	s.display();
	cout << s.search(3) << endl;
	s.insert(2, "123");
	s.display();
	s.remove(2, 4);
	s.display();
	s.update(2, 4, "123");
	s.display();
	s.update(2, 4, "1234");
	s.display();
	s.update(2, 5, "123");
	s.display();
	system("pause");
    return 0;
}