title: How to get the sorted index of a vector?
body: <p>I have a vector. It is not sorted. Now I want to get its indices which will sort the vector. For example <code>vector&lt;int&gt; v{1, 3, 2}</code>, sorted indices are <code>{0, 2, 1}</code> because <code>v[0] &lt;= v[2] &lt;= v[1]</code>. If two equal, doesn't matter which one go first.</p>