Find Doubles

This coding exercise is worth a total of $10$ points, each test is worth one point.

Given a list of $N$ integers, not necessarily unique, find all elements of the list for which there exists exactly one element of the list which is twice that number. The integers range from $0$ to $1000.$ The list has no more than $100,000$ elements.

Your code should find the appropriate values and print them to STDOUT in sorted order.

Examples:

$1,2,3,4,5,6,7,8,9,0,8,,0,1,2,3$

$(8$ is $4^{***}2,$ but $8$ is present twice; $0$ is its own double, so it's part of the result$)$

$71711123$

$($nothing is exactly twice another element$)$

$1,1211$

$(1$ and $1$ both have their double $2$ present, and $2$ is present in the list only once$)$