问题
Referring to this question: How to subtract dates from each other
In Groovy, I've got a script that spits out the 5 largest values from a text file collection. How can I know what the indices of those values are?
回答1:
If you have a list of things ie:
def list = [ 'c', 'a', 'b' ]
One way of knowing the original index would be to use transpose() to join this list to a counter, then sort the new list, then you will have a sorted list with the original index as the secondary element
ie:
[list,0..<list.size()].transpose().sort { it[0] }.each { item, index ->
println "$item (was at position $index)"
}
To break that down;
[list,0..<list.size()]
gives us (effectively) a new list [ [ 'c', 'a', 'b' ], [ 0, 1, 2 ] ]
calling transpose() on this gives us: [ [ 'c', 0 ], [ 'a', 1 ], [ 'b', 2 ] ]
We then sort the list based on the first item in each element (the letters from our original list) with sort { it[0] }
And then iterate through each, printing out our now sorted item, and its original index location
回答2:
If the values are unique, you might just use the indexof method over the original list. For example, if you have the list:
def list = [4, 8, 0, 2, 9, 5, 7, 3, 6, 1]
And you know how to get the 5 largest values:
def maxVals = list.sort(false, {-it}).take 5 // This list will be [9, 8, 7, 6, 5]
You can then do:
def indexes = maxVals.collect { list.indexOf it }
println indexes
And it will print:
[4, 1, 6, 8, 5]
来源：https://stackoverflow.com/questions/8087873/how-to-know-the-indices-of-values-in-collection