程序设计与算法（三）C++面向对象程序设计 第四周题目讲解

001:MyString

很经典的题目，考察深拷贝，运算符重载

#include <iostream>
#include <string>
#include <cstring>
using namespace std;
class MyString {
	char* p;
public:
	MyString(const char* s) {
		if (s) {
			p = new char[strlen(s) + 1];
			strcpy(p, s);
		}
		else
			p = NULL;
	}
	~MyString() { if (p) delete[] p; }

	MyString(const MyString& s) {              // 拷贝构造
		if (s.p) {
			p = new char[strlen(s.p) + 1];
			strcpy(p, s.p);
		}
		else
			p = NULL;
	}

	void Copy(const char* s) {
		if (s == p) return;
		delete[] p;
		p = new char[strlen(s) + 1];
		strcpy(p, s);
	}

	MyString& operator = (const char* s) {
		if (p == s) return *this;
		delete[] p;
		p = new char[strlen(s) + 1];
		strcpy(p, s);
		return *this;
	}

	MyString& operator = (const MyString& s) {
		if (p == s.p) return *this;
		delete[] p;
		p = new char[strlen(s.p) + 1];
		strcpy(p, s.p);
		return *this;
	}

	friend ostream& operator<<(o