C++第9周项目 动态存储分配及深复制 【项目1-深复制体验】(复习新版)

/*

*copyright(c) 2016,烟台大学计算机学院

*All rights reserved

*文件名称：test.cpp

*作者：谭泽纯

*版本：v6.0

*

*问题描述：

（1）阅读下面的程序，补足未完成的注释

<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include<iostream></span>
<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include<cstring></span>
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">using</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">namespace</span> <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">std</span>;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">class</span> A
{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">private</span>:
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *a;
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">public</span>:
A(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *aa)
{
a = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span>[<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strlen</span>(aa)+<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>];  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//（a）这样处理的意义在于：______________________________</span>
<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">strcpy</span>(a, aa);  <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//（b）数据成员a与形式参数aa的关系：___________________________________</span>
}
~A()
{
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">delete</span> []a;   <span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//（c）这样处理的意义在于：  ___________________________________________</span>
}
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> output() { <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">cout</span><<a<<endl; }
};
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">int</span> main(){
A a(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"good morning, code monkeys!"</span>);
a.output();
A b(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"good afternoon, codes!"</span>);
b.output();
<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">return</span> <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;
}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right; background-color: rgb(238, 238, 238);"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li><li style="box-sizing: border-box; padding: 0px 5px;">12</li><li style="box-sizing: border-box; padding: 0px 5px;">13</li><li style="box-sizing: border-box; padding: 0px 5px;">14</li><li style="box-sizing: border-box; padding: 0px 5px;">15</li><li style="box-sizing: border-box; padding: 0px 5px;">16</li><li style="box-sizing: border-box; padding: 0px 5px;">17</li><li style="box-sizing: border-box; padding: 0px 5px;">18</li><li style="box-sizing: border-box; padding: 0px 5px;">19</li><li style="box-sizing: border-box; padding: 0px 5px;">20</li><li style="box-sizing: border-box; padding: 0px 5px;">21</li><li style="box-sizing: border-box; padding: 0px 5px;">22</li><li style="box-sizing: border-box; padding: 0px 5px;">23</li><li style="box-sizing: border-box; padding: 0px 5px;">24</li><li style="box-sizing: border-box; padding: 0px 5px;">25</li><li style="box-sizing: border-box; padding: 0px 5px;">26</li></ul>

（2）将注释（a）所在的那一行去掉，会出现什么现象？为什么？为什么a数据成员所占用的存储空间要在aa长度基础上加1？若指针a不是指向字符（即不作为字符串的地址），是否有必要加1？

#include<iostream>

#include<cstring>

using namespace std;

class A

{

private:

char *a;

public:

A(char *aa)

{

a = new char[strlen(aa)+1]; //（a）这样处理的意义在于：_为a建立内存空间

strcpy(a, aa); //（b）数据成员a与形式参数aa的关系：相等

}

A(A&s)

{

a=new char[strlen(s.a)+1];

strcpy(a,s.a);

}

~A()

{

delete []a; //（c）这样处理的意义在于： 删除内存空间，防止浪费内存

}

void output() { cout<<a<<endl; }

};

int main()

{

A a("good morning, code monkeys!");

a.output();

A b(a);

b.output();

return 0;

}