title: Convert a number to a string with specified length in C++
body: <p>I have some numbers of different length (like 1, 999, 76492, so on) and I want to convert them all to strings with a common length (for example, if the length is 6, then those strings will be: '000001', '000999', '076492'). </p>
  
  <p>In other words, I need to add correct amount of leading zeros to the number.</p>
  
  <pre><code>int n = 999;
  string str = some_function(n,6);
  //str = '000999'
  </code></pre>
  
  <p>Is there a function like this in C++?</p>