Groovy: find all elements in a list equal to the max element

Question

Is there any simpler way to find all elements in a list that are equal to the max element.

List v = [ 1,2,3,4,5,5  ]
def max = v.max()
def maxs = v.findAll { it == max }

Thanks!

Answer 1

How you've done it for the simple example is exactly how I would do it. I may use groupBy if I was dealing with a more complex object.

    List v = [ 1,2,3,4,5,5 ]
    def max = v.max()
    def results = v.groupBy {it}.get(max)
    assert [5,5] == results

Answer 2

In your code you go two times over your list (one time for the method List.max and one time for the method List.findAll). Of course this is acceptable, if you just have a small list. If your list is very large, you should go through it just one time.

When your list just contains primitives, it is enough to store the maximum and the count of this maximum in one variable, to go through the list and update both variables:

    def list = [1,2,3,4,5,5]
    def max = null
    def count = 0

    for (int i: list) {
        if (max == null || i > max) {
            max = i
            count = 1
        } else if (i == max) {
            count++
        }
    }

    println max // 5
    println count // 2

Of course the above code has more lines than yours, but should be faster for very large lists.

Answer 3

I think this way is the most convenient one:

def v = [ 1,2,3,4,5,5 ]
v = v.groupBy { it }.sort { 0 - it.key }.values()
assert [[5,5], [4], [3], [2], [1]] == v