sort coordinates by x value
<p>I have following code:</p>

<pre><code>#include &lt;vector&gt;
using namespace std;
struct Point
{
  int x, y;
};
bool Sort(struct Point&amp; a,struct  Point&amp; b){
  return a.x&lt;b.x;
}
int main(int argc, char *argv[])
{
  vector&lt;Point&gt;a;
  for (int i=0;i&lt;10;i++){
    cin&gt;&gt;a[i].x&gt;&gt;a[i].y;
  }
  sort(a,10,Sort);
  system("PAUSE");
  return EXIT_SUCCESS;
}
</code></pre>

<p>but it seems wrong. Can you please tell me the correct form of the sort function to use?</p>
