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Java/HeapSort.java at master · rcanto/Java · GitHub
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HeapSort.java
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import
java
.
util
.
Scanner
;
/**
* Heap Sort Algorithm. Implements MinHeap
*
*/
public
class
HeapSort
{
/**
* array to store heap.
*/
private
int
[]
heap
;
/**
* size of heap.
*/
private
int
size
;
/**
* Constructor.
*
* @param heap
* array of unordered integers
*/
public
HeapSort
(
int
[]
heap
) {
this
.
setHeap
(
heap
);
this
.
setSize
(
heap
.
length
);
}
/**
* Sets this.size with {@code length).
*
* @param length
* integer length of heap
*/
private
void
setSize
(
int
length
) {
this
.
size
=
length
;
}
/**
* Sets Heap with {@code heap}.
*
* @param heap
* array of unordered elements
*/
private
void
setHeap
(
int
[]
heap
) {
this
.
heap
=
heap
;
}
/**
* Swaps index of {@code first} with {@code second}.
*
* @param first
* index to swap {@code second} with
* @param second
* index to swap {@code first} with
*/
private
void
swap
(
int
first
,
int
second
) {
int
temp
=
this
.
heap
[
first
];
this
.
heap
[
first
] =
this
.
heap
[
second
];
this
.
heap
[
second
] =
temp
;
}
/**
* Heapifies subtree from {@code top} as root to {@code last} as last child.
*
* @param rootIndex
* index of root
* @param lastChild
* index of last child
*/
private
void
heapSubtree
(
int
rootIndex
,
int
lastChild
) {
int
leftIndex
=
rootIndex
*
2
+
1
;
int
rightIndex
=
rootIndex
*
2
+
2
;
int
root
=
this
.
heap
[
rootIndex
];
if
(
rightIndex
<=
lastChild
) {
// if has right and left children
int
left
=
this
.
heap
[
leftIndex
];
int
right
=
this
.
heap
[
rightIndex
];
if
(
left
<
right
&&
left
<
root
) {
this
.
swap
(
leftIndex
,
rootIndex
);
this
.
heapSubtree
(
leftIndex
,
lastChild
);
}
else
if
(
right
<
root
) {
this
.
swap
(
rightIndex
,
rootIndex
);
this
.
heapSubtree
(
rightIndex
,
lastChild
);
}
}
else
if
(
leftIndex
<=
lastChild
) {
// if no right child, but has left child
int
left
=
this
.
heap
[
leftIndex
];
if
(
left
<
root
) {
this
.
swap
(
leftIndex
,
rootIndex
);
this
.
heapSubtree
(
leftIndex
,
lastChild
);
}
}
}
/**
* Makes heap with {@code root} as root.
*
* @param root
* index of root of heap
*/
private
void
makeMinHeap
(
int
root
) {
int
leftIndex
=
root
*
2
+
1
;
int
rightIndex
=
root
*
2
+
2
;
boolean
hasLeftChild
=
leftIndex
<
this
.
heap
.
length
;
boolean
hasRightChild
=
rightIndex
<
this
.
heap
.
length
;
if
(
hasRightChild
) {
//if has left and right
this
.
makeMinHeap
(
leftIndex
);
this
.
makeMinHeap
(
rightIndex
);
this
.
heapSubtree
(
root
,
this
.
heap
.
length
-
1
);
}
else
if
(
hasLeftChild
) {
this
.
heapSubtree
(
root
,
this
.
heap
.
length
-
1
);
}
}
/**
* Gets the root of this.heap.
*
* @return root of this.heap
*/
private
int
getRoot
() {
this
.
swap
(
0
,
this
.
size
-
1
);
this
.
size
--;
this
.
heapSubtree
(
0
,
this
.
size
-
1
);
return
this
.
heap
[
this
.
size
];
// return old root
}
/**
* Sorts this.heap with heap sort; displays ordered elements to console.
*
* @return {@code sorted} array of sorted elements
*/
public
final
int
[]
sort
() {
this
.
makeMinHeap
(
0
);
// make min heap using index 0 as root.
int
[]
sorted
=
new
int
[
this
.
size
];
int
index
=
0
;
while
(
this
.
size
>
0
) {
int
min
=
this
.
getRoot
();
sorted
[
index
] =
min
;
index
++;
}
return
sorted
;
}
/**
* Gets input to sort.
*
* @return unsorted array of integers to sort
*/
public
static
int
[]
getInput
() {
final
int
numElements
=
6
;
int
[]
unsorted
=
new
int
[
numElements
];
Scanner
input
=
new
Scanner
(
System
.
in
);
System
.
out
.
println
(
"Enter any 6 Numbers for Unsorted Array : "
);
for
(
int
i
=
0
;
i
<
numElements
;
i
++) {
unsorted
[
i
] =
input
.
nextInt
();
}
input
.
close
();
return
unsorted
;
}
/**
* Prints elements in heap.
*
* @param heap
* array representing heap
*/
public
static
void
printData
(
int
[]
heap
) {
System
.
out
.
println
(
"Sorted Elements:"
);
for
(
int
i
=
0
;
i
<
heap
.
length
;
i
++) {
System
.
out
.
print
(
" "
+
heap
[
i
] +
" "
);
}
}
/**
* Main method.
*
* @param args
* the command line arguments
*/
public
static
void
main
(
String
[]
args
) {
int
[]
heap
=
getInput
();
HeapSort
data
=
new
HeapSort
(
heap
);
int
[]
sorted
=
data
.
sort
();
printData
(
sorted
);
}
}
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