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insert [C++ Reference]
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<h2><a name="insert" id="insert">insert</a></h2>
<div class="level2">
<p>
Syntax:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co2">#include <vector></span>
iterator insert<span class="br0">(</span> iterator loc<span class="sy0">,</span> <span class="kw4">const</span> TYPE<span class="sy0">&</span> val <span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">void</span> insert<span class="br0">(</span> iterator loc<span class="sy0">,</span> size_type num<span class="sy0">,</span> <span class="kw4">const</span> TYPE<span class="sy0">&</span> val <span class="br0">)</span><span class="sy0">;</span>
<span class="kw4">void</span> insert<span class="br0">(</span> iterator loc<span class="sy0">,</span> input_iterator start<span class="sy0">,</span> input_iterator end <span class="br0">)</span><span class="sy0">;</span></pre>
<p>
The insert method either:
</p>
<ul>
<li class="level1"><div class="li"> inserts <code>val</code> before <code>loc</code>, returning an iterator to the element inserted,</div>
</li>
<li class="level1"><div class="li"> inserts <code>num</code> copies of <code>val</code> before <code>loc</code>, or</div>
</li>
<li class="level1"><div class="li"> inserts the elements from <code>start</code> to <code>end</code> before <code>loc</code>.</div>
</li>
</ul>
<p>
Note that inserting elements into a vector can be relatively time-intensive,
since the underlying data structure for a vector is an array. In order to
insert data into an array, you might need to displace a lot of the elements of
that array, and this can take <a href="../../complexity.html" class="wikilink1" title="complexity">linear time</a>. If you are planning on doing a lot
of insertions into your vector and you care about speed, you might be better
off using a container that has a linked list as its underlying data structure
(such as a <a href="../../stl/list/start.html" class="wikilink1" title="stl:list:start">list</a> or a <a href="../../stl/deque/start.html" class="wikilink1" title="stl:deque:start">deque</a>).
</p>
<p>
For example, the following code uses the insert() function to splice four
copies of the character 'C' into a vector of characters:
</p>
<pre class="c code c++" style="font-family:monospace;"> <span class="co1">// Create a vector, load it with the first 10 characters of the alphabet</span>
vector<span class="sy0"><</span>char<span class="sy0">></span> alphaVector<span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> <span class="kw4">int</span> i<span class="sy0">=</span><span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> <span class="nu0">10</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <span class="br0">{</span>
alphaVector.<span class="me1">push_back</span><span class="br0">(</span> i <span class="sy0">+</span> <span class="st0">'A'</span> <span class="br0">)</span><span class="sy0">;</span>
<span class="br0">}</span>
<span class="co1">// Insert four C's into the vector</span>
vector<span class="sy0"><</span>char<span class="sy0">>::</span><span class="me2">iterator</span> theIterator <span class="sy0">=</span> alphaVector.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span>
alphaVector.<span class="me1">insert</span><span class="br0">(</span> theIterator<span class="sy0">,</span> <span class="nu0">4</span><span class="sy0">,</span> <span class="st0">'C'</span> <span class="br0">)</span><span class="sy0">;</span>
<span class="co1">// Display the vector</span>
<span class="kw1">for</span><span class="br0">(</span> theIterator <span class="sy0">=</span> alphaVector.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> theIterator <span class="sy0">!=</span> alphaVector.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> <span class="sy0">++</span>theIterator <span class="br0">)</span> <span class="br0">{</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="sy0">*</span>theIterator<span class="sy0">;</span>
<span class="br0">}</span></pre>
<p>
This code would display:
</p>
<pre class="code">
CCCCABCDEFGHIJ</pre>
<p>
Here is another example of the insert method. In this code, insert is
used to append the contents of one vector into the end of another:
</p>
<pre class="c code c++" style="font-family:monospace;"> vector<span class="sy0"><</span>int<span class="sy0">></span> v1<span class="sy0">;</span>
v1.<span class="me1">push_back</span><span class="br0">(</span> 0 <span class="br0">)</span><span class="sy0">;</span>
v1.<span class="me1">push_back</span><span class="br0">(</span> 1 <span class="br0">)</span><span class="sy0">;</span>
v1.<span class="me1">push_back</span><span class="br0">(</span> 2 <span class="br0">)</span><span class="sy0">;</span>
v1.<span class="me1">push_back</span><span class="br0">(</span> 3 <span class="br0">)</span><span class="sy0">;</span>
vector<span class="sy0"><</span>int<span class="sy0">></span> v2<span class="sy0">;</span>
v2.<span class="me1">push_back</span><span class="br0">(</span> 5 <span class="br0">)</span><span class="sy0">;</span>
v2.<span class="me1">push_back</span><span class="br0">(</span> 6 <span class="br0">)</span><span class="sy0">;</span>
v2.<span class="me1">push_back</span><span class="br0">(</span> 7 <span class="br0">)</span><span class="sy0">;</span>
v2.<span class="me1">push_back</span><span class="br0">(</span> 8 <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"Before, v2 is: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> vector<span class="sy0"><</span>int<span class="sy0">>::</span><span class="me2">size_type</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> v2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <span class="br0">{</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> v2<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<span class="br0">}</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> endl<span class="sy0">;</span>
v2.<span class="me1">insert</span><span class="br0">(</span> v2.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> v1.<span class="me1">begin</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">,</span> v1.<span class="me1">end</span><span class="br0">(</span><span class="br0">)</span> <span class="br0">)</span><span class="sy0">;</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> <span class="st0">"After, v2 is: "</span><span class="sy0">;</span>
<span class="kw1">for</span><span class="br0">(</span> vector<span class="sy0"><</span>int<span class="sy0">>::</span><span class="me2">size_type</span> i <span class="sy0">=</span> <span class="nu0">0</span><span class="sy0">;</span> i <span class="sy0"><</span> v2.<span class="me1">size</span><span class="br0">(</span><span class="br0">)</span><span class="sy0">;</span> i<span class="sy0">++</span> <span class="br0">)</span> <span class="br0">{</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> v2<span class="br0">[</span>i<span class="br0">]</span> <span class="sy0"><<</span> <span class="st0">" "</span><span class="sy0">;</span>
<span class="br0">}</span>
<a href="http://www.opengroup.org/onlinepubs/009695399/functions/cout.html"><span class="kw3">cout</span></a> <span class="sy0"><<</span> endl<span class="sy0">;</span></pre>
<p>
When run, this code displays:
</p>
<pre class="code">
Before, v2 is: 5 6 7 8
After, v2 is: 5 6 7 8 0 1 2 3</pre>
<p>
Related Topics: <a href="../../stl/vector/assign.html" class="wikilink1" title="stl:vector:assign">assign</a>, <a href="../../stl/vector/erase.html" class="wikilink1" title="stl:vector:erase">erase</a>, <a href="../../stl/vector/push_back.html" class="wikilink1" title="stl:vector:push_back">push_back</a>, <span class="curid"><a href="../../stl/vector/insert.html" class="wikilink1" title="stl:vector:insert">insert</a></span>
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