Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p><code>vec.begin()</code> and <code>vec.end()</code> do not return the first and last elements of the <code>vector</code>. They actually return what is known as an <em>iterator</em>. An iterator behaves very much like a pointer to the elements. If you have an iterator <code>i</code> that you initialised with <code>vec.begin()</code>, you can get a pointer to the second element in the vector just by doing <code>i++</code> - the same as you would if you had a point to the first element in an array. Likewise you can do <code>i--</code> to go backwards. For some iterators (known as random access iterators), you can even do <code>i + 5</code> to get an iterator to the 5th element after <code>i</code>.</p> <p>This is how the algorithm accesses the container. It knows that all of the elements that it should be sorting are between <code>begin()</code> and <code>end()</code>. It navigates around the elements by doing simple iterator operations. It can then modify the elements by doing <code>*i</code>, which gives the algorithm a reference to the element that <code>i</code> is pointing at. For example, if <code>i</code> is set to <code>vec.begin()</code>, and you do <code>*i = 5;</code>, you will change the value of the first element of <code>vec</code>.</p> <p>This approach allows you to pass only <em>part</em> of a <code>vector</code> to be sorted. Let's say you only wanted to sort the first 5 elements of your <code>vector</code>. You could do:</p> <pre><code>std::sort(vec.begin(), vec.begin() + 5); </code></pre> <p>This is very powerful. Since iterators behave very much like pointers, you can actually pass plain old pointers too. Let's say you have an array <code>int array[] = {4, 3, 2, 5, 1};</code>, you could easily call <code>std::sort(array, array + 5)</code> (because the name of an array will decay to a pointer to its first element).</p>
    singulars
    1. This table or related slice is empty.
    1. POHow does sorting in c++ work?
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USJoseph Mansfield
    1. USJoseph Mansfield
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThat actually makes sense."because the name of an array will decay to a pointer to its first element", I think that's actually the case with MIPS assembly code too --- Thank you very much
      singulars
      1. PO
      1. USAdeeb
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload