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Sorting algorithms/Heapsort: Difference between revisions
→{{header|Groovy}}: added a better to read and commented version of the code.
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imported>SerErris (→{{header|Groovy}}: added a better to read and commented version of the code.) |
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list
}</syntaxhighlight>
This is a better to read version. It includes comments and much better to understand and read function headers and loops.
It also has better readable variable names and can therefore be better used for study purposes.
It contains the same functions, even if a function with a single variable assignment in it is not very useful.
<syntaxhighlight lang="groovy">
def makeSwap (list, element1, element2) {
//exchanges two elements in a list.
//print a dot for each swap.
print "."
list[[element2,element1]] = list[[element1,element2]]
}
def checkSwap (list, child, parent) {
//check if parent is smaller than child, then swap.
if (list[parent] < list[child]) makeSwap(list, child, parent)
}
def siftDown (list, start, end) {
//end represents the limit of how far down the heap to sift
//start is the head of the heap
def parent = start
while (parent*2 < end) { //While the root has at least one child
def child = parent*2 + 1 //root*2+1 points to the left child
//find the child with the higher value
//if the child has a sibling and the child's value is less than its sibling's..
if (child + 1 <= end && list[child] < list[child+1]) child++ //point to the other child
if (checkSwap(list, child, parent)) { //check if parent is smaller than child and swap
parent = child //make child to next parent
} else {
return //The rest of the heap is in order - return.
}
}
}
def heapify (list) {
// Create a heap out of a list
// run through all the heap parents and
// ensure that each parent is lager than the child for all parent/childs.
// (list.size() -2) / 2 = last parent in the heap.
((list.size() - 2).intdiv(2)..0).each {start ->
siftDown(list, start, list.size() - 1)
}
}
def heapSort (list) {
//heap sort any unsorted list
heapify(list) //ensure that the list is in a binary heap state
//Run the list backwards and
//for end = (size of list -1 ) to 0
((list.size()-1)..0).each { end ->
makeSwap(list, 0, end) //put the top of the heap to the end (largest element)
siftDown(list, 0, end-1) //ensure that the rest is a heap again
}
list
}</syntaxhighlight>
Test:
<syntaxhighlight lang="groovy">println (heapSort([23,76,99,58,97,57,35,89,51,38,95,92,24,46,31,24,14,12,57,78,4]))
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