12. sortByHeight

Some people are standing in a row in a park. There are trees between them which cannot be moved. Your task is to rearrange the people by their heights in a non-descending order without moving the trees.

Example

For a = [-1, 150, 190, 170, -1, -1, 160, 180], the output should be
sortByHeight(a) = [-1, 150, 160, 170, -1, -1, 180, 190].

Code

function sortByHeight(a) {

}