JSDomHighlight

function solve(selector) {
    let targetLimit = 0;
    function scan(target) {
        let children = $(target).children();
        if (children.length == 0)
            return target;
        let childWithMostChildren, maxChildrenCount = Number.NEGATIVE_INFINITY;
        for (let i = 0; i < children.length; i++) {
            if ($(children[i]).children().length > maxChildrenCount) {
                maxChildrenCount = $(children[i]).children().length;
                childWithMostChildren = i;
            }
        }
        targetLimit++;
        return scan(children[childWithMostChildren]);
    }
    let deepestNode = scan(selector);
    $(deepestNode).addClass('highlight');
    let targets = $(deepestNode).parents();
    for (let i = 0; i < targets.length && i < targetLimit; i++)
        $(targets[i]).addClass('highlight');
}