习题3.15 .html

c++ primer 答案（第4版） 自己整理的 只有1-5章

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; }</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; if (ivec.size() % 2 != 0) //提示最后一个元素没有求和</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; endl </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&lt;&lt;
&quot;The last element is not been summed &quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&lt;&lt; &quot;and its value is &quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&lt;&lt;
*(ivec.end()-1) &lt;&lt; endl;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; return 0;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>}</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//读一组整数到vector对象，计算首尾配对元素的和并输出</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//使用迭代器访问vector中的元素</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;iostream&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;vector&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>using namespace std;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>int main()</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>{</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; vector&lt;int&gt; ivec;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; int ival;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; //读入数据到vector对象</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; cout &lt;&lt; &quot;Enter numbers(Ctrl+Z
to end):&quot; &lt;&lt; endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; while (cin&gt;&gt;ival)</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ivec.push_back(ival);</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; //计算首尾配对元素的和并输出</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; if (ivec.size() == 0) {</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; &quot;No element?!&quot; &lt;&lt; endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return
-1;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; }</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; cout &lt;&lt; &quot;Sum of each
pair of counterpart elements in the vector:&quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&lt;
endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; vector&lt;int&gt;::size_type
cnt=0;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; for (vector&lt;int&gt;::iterator
first = ivec.begin(), </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;last
= ivec.end() - 1;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;first
&lt; last; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;++first,
--last) {</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; *first + *last &lt;&lt; &quot;\t&quot;;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; ++cnt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; if ( cnt
% 6 == 0) //每行输出6个和</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; }</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; if (first == last) //提示居中元素没有求和</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; endl </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&lt;
&quot;The center element is not been summed &quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&lt;
&quot;and its value is &quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &lt;&lt;
*first &lt;&lt; endl;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; return 0;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>}</p>



<p class=MsoNormal align=left style='text-align:left;text-autospace:none'>重做习题3.14如下：</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//读入一段文本到vector对象，每个单词存储为vector中的一个元素。</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//把vector对象中每个单词转化为大写字母。</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//输出vector对象中转化后的元素，每8个单词为一行输出。</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>//使用迭代器访问vector中的元素</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;iostream&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;string&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;vector&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>#include &lt;cctype&gt;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>using namespace std;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>int main()</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>{</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; vector&lt;string&gt; svec;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; string str;</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; //读入文本到vector对象</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; cout &lt;&lt; &quot;Enter text(Ctrl+Z
to end):&quot; &lt;&lt; endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; while (cin&gt;&gt;str)</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; svec.push_back(str);</p>



<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; //将vector对象中每个单词转化为大写字母,并输出</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; if (svec.size() == 0) {</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cout
&lt;&lt; &quot;No string?!&quot; &lt;&lt; endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; return
-1;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; }</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; cout &lt;&lt; &quot;Transformed
elements from the vector:&quot; </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; &nbsp;&lt;&lt;
endl;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; vector&lt;string&gt;::size_type
cnt = 0;</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; for
(vector&lt;string&gt;::iterator iter = svec.begin(); </p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;
punctuation-trim:none;text-autospace:none'>&nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp;&nbsp; iter !=
svec.end(); ++iter) {</p>

<p class=MsoNormal align=left style='text-align:left;line-height:8.8pt;