138 lines
11 KiB
HTML
138 lines
11 KiB
HTML
<!DOCTYPE html>
|
|
<html lang="zh" dir="ltr" class="client-nojs" xmlns="http://www.w3.org/1999/xhtml" xml:lang="zh">
|
|
<head><meta http-equiv="x-ua-compatible" content="ie=edge">
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<title>std::vector<T,Allocator>::shrink_to_fit</title>
|
|
<link rel="stylesheet" href="ext.css" />
|
|
<link rel="stylesheet" href="site_modules.css" />
|
|
</head>
|
|
<body class="mediawiki ltr sitedir-ltr ns-0 ns-subject page-cpp_container_vector_shrink_to_fit skin-cppreference2 action-view cpp-page-template cpp-navbar">
|
|
<div id="cpp-content-base">
|
|
<div id="content"><a id="top"></a>
|
|
<h1 id="firstHeading" class="firstHeading"><span style="font-size:0.7em; line-height:130%">std::vector<T,Allocator>::</span>shrink_to_fit</h1>
|
|
<div id="bodyContent">
|
|
<div id="contentSub"><span class="subpages">< <a href="cpp.html">cpp</a>‎ | <a href="cpp-container.html">container</a>‎ | <a href="cpp-container-vector.html">vector</a></span></div>
|
|
<div id="mw-content-text" lang="zh" dir="ltr" class="mw-content-ltr" xml:lang="zh">
|
|
<div class="t-page-template" style="">
|
|
<p></p>
|
|
</div>
|
|
<table class="t-dcl-begin">
|
|
<tbody></tbody>
|
|
<tbody class="t-dcl-rev">
|
|
<tr class="t-dcl t-since-cxx11 t-until-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">void</span> shrink_to_fit<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx11">(C++11 起)</span><br />
|
|
<span class="t-mark-rev t-until-cxx20">(C++20 前)</span></td>
|
|
</tr>
|
|
<tr class="t-dcl t-since-cxx20">
|
|
<td>
|
|
<div><span class="mw-geshi cpp source-cpp"><span class="kw4">constexpr</span> <span class="kw4">void</span> shrink_to_fit<span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span></span></div>
|
|
</td>
|
|
<td class="t-dcl-nopad"></td>
|
|
<td><span class="t-mark-rev t-since-cxx20">(C++20 起)</span></td>
|
|
</tr>
|
|
</tbody>
|
|
<tbody>
|
|
<tr class="t-dcl-sep">
|
|
<td></td>
|
|
<td></td>
|
|
<td></td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<p>请求移除未使用的容量。</p>
|
|
<p>它是减少 <span class="t-lc"><a href="cpp-container-vector-capacity.html">capacity()</a></span> 到 <span class="t-lc"><a href="cpp-container-vector-size.html">size()</a></span>非强制性请求。请求是否达成依赖于实现。</p>
|
|
<p>若发生重分配，则所有迭代器，包含尾后迭代器，和所有到元素的引用都被非法化。若不发生重分配，则没有迭代器或引用被非法化。</p>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E6.95.B0">参数</span></h3>
|
|
<p>（无）</p>
|
|
<table class="t-par-begin">
|
|
<tr class="t-par-hitem">
|
|
<td colspan="3">类型要求</td>
|
|
</tr>
|
|
<tr class="t-par-req">
|
|
<td colspan="3">-
|
|
<div class="spacer"></div>
|
|
<code>T</code> 必须满足<a href="cpp-named_req-MoveInsertable.html"><span style="font-style:italic">可移动插入</span> <span style="font-family: Georgia, 'DejaVu Serif', serif; font-style:italic">(MoveInsertable)</span></a> 的要求。</td>
|
|
</tr>
|
|
</table>
|
|
<h3><span class="mw-headline" id=".E8.BF.94.E5.9B.9E.E5.80.BC">返回值</span></h3>
|
|
<p>（无）</p>
|
|
<h3><span class="mw-headline" id=".E5.A4.8D.E6.9D.82.E5.BA.A6">复杂度</span></h3>
|
|
<p>至多与容器大小成线性。</p>
|
|
<h3><span class="mw-headline" id=".E6.B3.A8.E8.A7.A3">注解</span></h3>
|
|
<p>若 <code>T</code> 的移动构造函数以外的操作抛出异常，则无效果。</p>
|
|
<h3><span class="mw-headline" id=".E7.A4.BA.E4.BE.8B">示例</span></h3>
|
|
<div class="t-template-editlink" style=""></div>
|
|
<div class="t-example">
|
|
<div class="t-example-live-link"></div>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="cpp source-cpp">
|
|
<pre class="de1"><span class="co2">#include <iostream></span>
|
|
<span class="co2">#include <vector></span>
|
|
|
|
<span class="kw4">int</span> main<span class="br0">(</span><span class="br0">)</span>
|
|
<span class="br0">{</span>
|
|
<a href="cpp-container-vector.html"><span class="kw1269">std::<span class="me2">vector</span></span></a><span class="sy1"><</span><span class="kw4">int</span><span class="sy1">></span> v<span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Default-constructed capacity is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">resize</span><span class="br0">(</span><span class="nu0">100</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity of a 100-element vector is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">resize</span><span class="br0">(</span><span class="nu0">50</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after resize(50) is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">shrink_to_fit</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after shrink_to_fit() is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">clear</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after clear() is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">shrink_to_fit</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after shrink_to_fit() is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="kw1">for</span> <span class="br0">(</span><span class="kw4">int</span> i <span class="sy1">=</span> <span class="nu0">1000</span><span class="sy4">;</span> i <span class="sy1"><</span> <span class="nu0">1300</span><span class="sy4">;</span> <span class="sy2">++</span>i<span class="br0">)</span>
|
|
v.<span class="me1">push_back</span><span class="br0">(</span>i<span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after adding 300 elements is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
v.<span class="me1">shrink_to_fit</span><span class="br0">(</span><span class="br0">)</span><span class="sy4">;</span>
|
|
<a href="cpp-io-cout.html"><span class="kw1758">std::<span class="me2">cout</span></span></a> <span class="sy1"><<</span> <span class="st0">"Capacity after shrink_to_fit() is "</span> <span class="sy1"><<</span> v.<span class="me1">capacity</span><span class="br0">(</span><span class="br0">)</span> <span class="sy1"><<</span> <span class="st0">'<span class="es1">\n</span>'</span><span class="sy4">;</span>
|
|
<span class="br0">}</span></pre></div>
|
|
</div>
|
|
<p>可能的输出：</p>
|
|
<div dir="ltr" class="mw-geshi" style="text-align: left;">
|
|
<div class="text source-text">
|
|
<pre class="de1">Default-constructed capacity is 0
|
|
Capacity of a 100-element vector is 100
|
|
Capacity after resize(50) is 100
|
|
Capacity after shrink_to_fit() is 50
|
|
Capacity after clear() is 50
|
|
Capacity after shrink_to_fit() is 0
|
|
Capacity after adding 300 elements is 512
|
|
Capacity after shrink_to_fit() is 300</pre></div>
|
|
</div>
|
|
</div>
|
|
<h3><span class="mw-headline" id=".E5.8F.82.E9.98.85">参阅</span></h3>
|
|
<table class="t-dsc-begin">
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-container-vector-size.html"><span class="t-lines"><span>size</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>返回容纳的元素数<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
<tr class="t-dsc">
|
|
<td>
|
|
<div class="t-dsc-member-div">
|
|
<div><a href="cpp-container-vector-capacity.html"><span class="t-lines"><span>capacity</span></span></a></div>
|
|
</div>
|
|
</td>
|
|
<td>返回当前存储空间能够容纳的元素数<br />
|
|
<span class="t-mark">(公开成员函数)</span></td>
|
|
</tr>
|
|
</table>
|
|
</div>
|
|
<div class="visualClear"></div>
|
|
</div>
|
|
</div>
|
|
</div>
|
|
</body>
|
|
</html>
|