📄 all.html
字号:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html><head> <meta name="generator" content= "HTML Tidy for Linux/x86 (vers 1 September 2005), see www.w3.org"> <title>C++ Queues</title> <link href="../cppreference.css" rel="stylesheet" type="text/css"></head><body><table> <tr> <td> <div class="body-content"> <div class="header-box"> <a href="../index.html">cppreference.com</a> > <a href= "index.html">C++ Queues</a> </div> <div class="name-format"> back </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> <a href="../containers.html">TYPE</a>& back(); const <a href="../containers.html">TYPE</a>& back() const;</pre> <p>The back() function returns a reference to the last element in the queue.</p> <p>For example:</p> <pre class="example-code"> queue<int> q; for( int i = 0; i < 5; i++ ) { q.push(i); } cout << "The first element is " << q.front() << " and the last element is " << q.back() << endl; </pre> <p>This code produces the following output:</p> <pre class="example-code"> The first element is 0 and the last element is 4 </pre> <p>The back() function runs in <a href="../complexity.html">constant time</a>.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="front.html">front</a><br> (C++ Lists) <a href="../cpplist/pop_back.html">pop_back</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> empty </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> bool empty() const;</pre> <p>The empty() function returns true if the queue has no elements, false otherwise.</p> <p>For example, the following code uses empty() as the stopping condition on a <a href= "../keywords/while.html">while</a> loop to clear a queue while displaying its contents:</p> <pre class="example-code"> queue<int> q; for( int i = 0; i < 5; i++ ) { q.push(i); } while( !q.empty() ) { cout << q.front() << endl; q.pop(); } </pre> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="size.html">size</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> front </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> <a href="../containers.html">TYPE</a>& front(); const <a href="../containers.html">TYPE</a>& front() const;</pre> <p>The front() function returns a reference to the first element of the queue, and runs in <a href="../complexity.html">constant time</a>.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="back.html">back</a><br> (C++ Lists) <a href="../cpplist/pop_front.html">pop_front</a><br> (C++ Lists) <a href="../cpplist/push_front.html">push_front</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> pop </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> void pop();</pre> <p>The function pop() removes the first element of the queue and discards it.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="push.html">push</a><br> (C++ Priority Queues) <a href= "../cpppriority_queue/top.html">top</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> push </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> void push( const <a href="../containers.html">TYPE</a>& val );</pre> <p>The function push() adds <em>val</em> to the end of the current queue.</p> <p>For example, the following code uses the push() function to add ten integers to the end of a queue:</p> <pre class="example-code"> queue<int> q; for( int i=0; i < 10; i++ ) { q.push(i); }</pre> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="pop.html">pop</a> </div> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> Queue constructor </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> queue(); queue( const Container& con );</pre> <p>Queues have a default constructor as well as a copy constructor that will create a new queue out of the container <em>con</em>. </p> <p>For example, the following code creates a queue of strings, populates it with input from the user, and then displays it back to the user:</p> <pre class="example-code"> queue<string> waiting_line; while( waiting_line.size() < 5 ) { cout << "Welcome to the line, please enter your name: "; string s; getline( cin, s ); waiting_line.push(s); } while( !waiting_line.empty() ) { cout << "Now serving: " << waiting_line.front() << endl; waiting_line.pop(); }</pre> <p>When run, the above code might produce this output:</p> <pre class="example-code"> Welcome to the line, please enter your name: Nate Welcome to the line, please enter your name: lizzy Welcome to the line, please enter your name: Robert B. Parker Welcome to the line, please enter your name: ralph Welcome to the line, please enter your name: Matthew Now serving: Nate Now serving: lizzy Now serving: Robert B. Parker Now serving: ralph Now serving: Matthew</pre> </div> </td> </tr> </table></body></html><hr> <div class="name-format"> size </div> <div class="syntax-name-format"> Syntax: </div> <pre class="syntax-box"> #include <queue> <strong>size_type</strong> size() const;</pre> <p>The size() function returns the number of elements in the current queue.</p> <div class="related-name-format"> Related topics: </div> <div class="related-content"> <a href="empty.html">empty</a><br> (C++ Strings) <a href="../cppstring/capacity.html">capacity</a><br> (C++ Strings) <a href="../cppstring/length.html">length</a><br> (C++ Multimaps) <a href= "../cppmultimap/max_size.html">max_size</a><br> (C++ Strings) <a href="../cppstring/resize.html">resize</a> </div> </div> </td> </tr> </table></body></html><hr></body></html>⌨️ 快捷键说明
复制代码
Ctrl + C
搜索代码
Ctrl + F
全屏模式
F11
切换主题
Ctrl + Shift + D
显示快捷键
?
增大字号
Ctrl + =
减小字号
Ctrl + -