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从www.CppReference.com打包的C++参考手册

  <p>For example, the following code puts 10 integers into a vector:</p>
  <pre class="example-code">
   vector&lt;int&gt; the_vector;
   for( int i = 0; i &lt; 10; i++ ) {
     the_vector.push_back( i );
   }     
</pre>

  <p>When displayed, the resulting vector would look like this:</p>
  <pre class="example-code">
 0 1 2 3 4 5 6 7 8 9            
</pre>

  <p>push_back() runs in <a href="../complexity.html">constant
  time</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="assign.html">assign</a><br>
    <a href="insert.html">insert</a><br>
    <a href="pop_back.html">pop_back</a><br>
    (C++ Lists) <a href="../cpplist/push_front.html">push_front</a>
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  <div class="name-format">
    rbegin
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  <a href="../iterators.html">reverse_iterator</a> rbegin();
  const_<a href=
"../iterators.html">reverse_iterator</a> rbegin() const;
</pre>

  <p>The rbegin() function returns a <a href=
  "../iterators.html">reverse_iterator</a> to the end of the current
  vector.</p>

  <p>rbegin() runs in <a href="../complexity.html">constant
  time</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="begin.html">begin</a><br>
    <a href="end.html">end</a><br>
    <a href="rend.html">rend</a>
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<hr>

  <div class="name-format">
    rend
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  <a href="../iterators.html">reverse_iterator</a> rend();
  const_<a href="../iterators.html">reverse_iterator</a> rend() const;
</pre>

  <p>The function rend() returns a <a href=
  "../iterators.html">reverse_iterator</a> to the beginning of the
  current vector.</p>

  <p>rend() runs in <a href="../complexity.html">constant time</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="begin.html">begin</a><br>
    <a href="end.html">end</a><br>
    <a href="rbegin.html">rbegin</a>
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<hr>

  <div class="name-format">
    reserve
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  void reserve( <strong>size_type</strong> size );
</pre>

  <p>The reserve() function sets the capacity of the vector to at least
  <em>size</em>.</p>

  <p>reserve() runs in <a href="../complexity.html">linear
  time</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="capacity.html">capacity</a>
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<hr>

  <div class="name-format">
    resize
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  void resize( <strong>size_type</strong> num, const <a href=
"../containers.html">TYPE</a>&amp; val = <a href=
"../containers.html">TYPE</a>() );
</pre>

  <p>The function resize() changes the size of the vector to
  <em>size</em>. If <em>val</em> is specified then any newly-created
  elements will be initialized to have a value of <em>val</em>.</p>

  <p>This function runs in <a href="../complexity.html">linear
  time</a>.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href=
    "vector_constructors.html">Vector constructors
    &amp; destructors</a><br>
    <a href="capacity.html">capacity</a><br>
    <a href="size.html">size</a>
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<hr>

  <div class="name-format">
    size
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  <strong>size_type</strong> size() const;
</pre>

  <p>The size() function returns the number of elements in the current
  vector.</p>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="capacity.html">capacity</a><br>
    <a href="empty.html">empty</a><br>
    (C++ Strings) <a href="../cppstring/length.html">length</a><br>
    <a href="max_size.html">max_size</a><br>
    <a href="resize.html">resize</a>
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<hr>

  <div class="name-format">
    swap
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  void swap( container&amp; from );
</pre>

  <p>The swap() function exchanges the elements of the current vector
  with those of <em>from</em>. This function operates in <a href=
  "../complexity.html">constant time</a>.</p>

  <p>For example, the following code uses the swap() function to
  exchange the contents of two vectors:</p>
  <pre class="example-code">
  vector<string> v1;
  v1.push_back("I'm in v1!");

  vector<string> v2;
  v2.push_back("And I'm in v2!");

  v1.swap(v2);

  cout << "The first element in v1 is " << v1.front() << endl;
  cout << "The first element in v2 is " << v2.front() << endl;
</pre>

  <p>The above code displays:</p>
  <pre class="example-code">
  The first element in v1 is And I'm in v2!
  The first element in v2 is I'm in v1!
</pre>

  <div class="related-name-format">
    Related topics:
  </div>

  <div class="related-content">
    <a href="vector_operators.html">= operator</a><br>
    (C++ Lists) <a href="../cpplist/splice.html">splice</a>
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<hr>

  <div class="name-format">
    Vector constructors
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  vector();
  vector( const vector&amp; c );
  vector( <strong>size_type</strong> num, const <a href=
"../containers.html">TYPE</a>&amp; val = <a href=
"../containers.html">TYPE</a>() );
  vector( <a href=
"../iterators.html">input_iterator</a> start, <a href=
"../iterators.html">input_iterator</a> end );
  ~vector();
</pre>

  <p>The default vector constructor takes no arguments, creates a new
  instance of that vector.</p>

  <p>The second constructor is a default copy constructor that can be
  used to create a new vector that is a copy of the given vector
  <em>c</em>.</p>

  <p>The third constructor creates a vector with space for <em>num</em>
  objects. If <em>val</em> is specified, each of those objects will be
  given that value. For example, the following code creates a vector
  consisting of five copies of the integer 42:</p>
  <pre class="example-code">
 vector&lt;int&gt; v1( 5, 42 );         
</pre>

  <p>The last constructor creates a vector that is initialized to
  contain the elements between <em>start</em> and <em>end</em>. For
  example:</p>
  <pre class="example-code">
 // create a vector of random integers
 cout &lt;&lt; &quot;original vector: &quot;;
 vector&lt;int&gt; v;
 for( int i = 0; i &lt; 10; i++ ) {
   int num = (int) rand() % 10;
   cout &lt;&lt; num &lt;&lt; &quot; &quot;;
   v.push_back( num );
 }
 cout &lt;&lt; endl;            

 // find the first element of v that is even
 vector&lt;int&gt;::iterator iter1 = v.begin();
 while( iter1 != v.end() &amp;&amp; *iter1 % 2 != 0 ) {
   iter1++;
 }              

 // find the last element of v that is even
 vector&lt;int&gt;::iterator iter2 = v.end();
 do {
   iter2--;
 } while( iter2 != v.begin() &amp;&amp; *iter2 % 2 != 0 );              

 // only proceed if we find both numbers
 if( iter1 != v.end() &amp;&amp; iter2 != v.begin() ) {
   cout &lt;&lt; &quot;first even number: &quot; &lt;&lt; *iter1 &lt;&lt; &quot;, last even number: &quot; &lt;&lt; *iter2 &lt;&lt; endl;         

   cout &lt;&lt; &quot;new vector: &quot;;
   vector&lt;int&gt; v2( iter1, iter2 );
   for( int i = 0; i &lt; v2.size(); i++ ) {
     cout &lt;&lt; v2[i] &lt;&lt; &quot; &quot;;
   }
   cout &lt;&lt; endl;
 }
</pre>

  <p>When run, this code displays the following output:</p>
  <pre class="example-code">
 original vector: 1 9 7 9 2 7 2 1 9 8
 first even number: 2, last even number: 8
 new vector: 2 7 2 1 9          
</pre>

  <p>All of these constructors run in <a href=
  "../complexity.html">linear time</a> except the first, which runs in
  <a href="../complexity.html">constant time</a>.</p>

  <p>The default destructor is called when the vector should be
  destroyed.</p>
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<hr>

  <div class="name-format">
    Vector operators
  </div>

  <div class="syntax-name-format">
    Syntax:
  </div>
  <pre class="syntax-box">
  #include &lt;vector&gt;
  <a href=
"../containers.html">TYPE</a>&amp; operator[]( <strong>size_type</strong> index );
  const <a href=
"../containers.html">TYPE</a>&amp; operator[]( <strong>size_type</strong> index ) const;
  vector operator=(const vector&amp; c2);
  bool operator==(const vector&amp; c1, const vector&amp; c2);
  bool operator!=(const vector&amp; c1, const vector&amp; c2);
  bool operator&lt;(const vector&amp; c1, const vector&amp; c2);
  bool operator&gt;(const vector&amp; c1, const vector&amp; c2);
  bool operator&lt;=(const vector&amp; c1, const vector&amp; c2);
  bool operator&gt;=(const vector&amp; c1, const vector&amp; c2);
</pre>

  <p>All of the C++ containers can be compared and assigned with the
  standard comparison operators: ==, !=, &lt;=, &gt;=, &lt;, &gt;, and
  =. Individual elements of a vector can be examined with the []
  operator.</p>

  <p>Performing a comparison or assigning one vector to another takes
  <a href="../complexity.html">linear time</a>. The [] operator runs in
  <a href="../complexity.html">constant time</a>.</p>

  <p>Two vectors are equal if:</p>

  <ol>
    <li>Their size is the same, and</li>

    <li>Each member in location i in one vector is equal to the the
    member in location i in the other vector.</li>
  </ol>

  <p>Comparisons among vectors are done lexicographically.</p>

  <p>For example, the following code uses the [] operator to access all
  of the elements of a vector:</p>
  <pre class="example-code">
 vector&lt;int&gt; v( 5, 1 );
 for( int i = 0; i &lt; v.size(); i++ ) {
   cout &lt;&lt; &quot;Element &quot; &lt;&lt; i &lt;&lt; &quot; is &quot; &lt;&lt; v[i] &lt;&lt; endl;
 }              
</pre>

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    Related topics:
  </div>

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    <a href="at.html">at</a>
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