堆排序(Java数组实现)
堆排序：利用大根堆
数组全部入堆，再出堆从后向前插入回数组中，数组就从小到大有序了。
public class MaxHeap<T extends Comparable<? super T>> {
private T[] data;
private int size;
private int capacity;
public MaxHeap(int capacity) {
this.data = (T[]) new Comparable[capacity + 1];
size = 0;
this.capacity = capacity;
}
public int size() {
return this.size;
}
public boolean isEmpty() {
return size == 0;
}
public int getCapacity() {
return this.capacity;
}
/**
* @return 查看最大根(只看不删, 与popMax对比)
*/
public T seekMax() {
return data[1];
}
public void swap(int i, int j) {
if (i != j) {
T temp = data[i];
data[i] = data[j];
data[j] = temp;
}
}
public void insert(T item) {
size++;
data[size] = item;
shiftUp(size);
}
/**
* @return 弹出最大根(弹出意味着删除, 与seekMax对比)
*/
public T popMax() {
swap(1, size--);
shiftDown(1);
return data[size + 1];
}
/**
* @param child 孩子节点下角标是child，父节点下角表是child/2
*/
public void shiftUp(int child) {
while (child > 1 && data[child].compareTo(data[child / 2]) > 0) {
swap(child, child / 2);
child = child / 2;
}
}
/**
* @param a data数组中某个元素的下角标
* @param b data数组中某个元素的下角标
* @return 哪个元素大就返回哪个的下角标
*/
private int max(int a, int b) {
if (data[a].compareTo(data[b]) < 0) {//如果data[b]大
return b;//返回b
} else {//如果data[a]大
return a;//返回a
}
}
/**
* @param a data数组中某个元素的下角标
* @param b data数组中某个元素的下角标
* @param c data数组中某个元素的下角标
* @return 哪个元素大就返回哪个的下角标
*/
private int max(int a, int b, int c) {
int biggest = max(a, b);
biggest = max(biggest, c);
return biggest;
}
/**
* @param father 父节点下角标是father,左右两个孩子节点的下角表分别是：father*2 和 father*2+1
*/
public void shiftDown(int father) {
while (true) {
int lchild = father * 2;//左孩子
int rchild = father * 2 + 1;//右孩子
int newFather = father;//newFather即将更新，父、左、右三个结点谁大，newFather就是谁的下角标
if (lchild > size) {//如果该father结点既没有左孩子，也没有右孩子
return;
} else if (rchild > size) {//如果该father结点只有左孩子，没有右孩子
newFather = max(father, lchild);
} else {//如果该father结点既有左孩子，又有右孩子
newFather = max(father, lchild, rchild);
}
if (newFather == father) {//说明father比两个子结点都要大，表名已经是大根堆，不用继续调整了
return;
} else {//否则，还需要继续调整堆，直到满足大根堆条件为止
swap(father, newFather);//值进行交换
father = newFather;//更新father的值，相当于继续调整shiftDown(newFather)
}
}
}
public static <T extends Comparable<? super T>> void sort(T[] arr) {
int len = arr.length;
//入堆
MaxHeap<T> maxHeap = new MaxHeap<T>(len);
for (int i = 0; i < len; i++) {
maxHeap.insert(arr[i]);
}
//出堆
for (int i = len - 1; i >= 0; i--) {
arr[i] = maxHeap.popMax();
}
}
public static void printArr(Object[] arr) {
for (Object o : arr) {
System.out.print(o);
System.out.print("\t");
}
System.out.println();
}
public static void main(String args[]) {
Integer[] arr = {3, 5, 1, 7, 2, 9, 8, 0, 4, 6};
printArr(arr);//3 5 1 7 2 9 8 0 4 6
sort(arr);
printArr(arr);//0 1 2 3 4 5 6 7 8 9
}
}
堆排序：对数组进行构造堆(最大堆)
public class MaxHeap<T extends Comparable<? super T>> {
private T[] data;
private int size;
private int capacity;
public MaxHeap(int capacity) {
this.capacity = capacity;
this.size = 0;
this.data = (T[]) new Comparable[capacity + 1];
}
public MaxHeap(T[] arr) {//heapify,数组建堆
capacity = arr.length;
data = (T[]) new Comparable[capacity + 1];
System.arraycopy(arr, 0, data, 1, arr.length);
size = arr.length;
for (int i = size / 2; i >= 1; i--) {
shiftDown(i);
}
}
public int size() {
return this.size;
}
public int getCapacity() {
return this.capacity;
}
public boolean isEmpty() {
return size == 0;
}
public T seekMax() {
return data[1];
}
public void swap(int i, int j) {
if (i != j) {
T temp = data[i];
data[i] = data[j];
data[j] = temp;
}
}
public void insert(T item) {
size++;
data[size] = item;
shiftUp(size);
}
public T popMax() {
swap(1, size--);
shiftDown(1);
return data[size + 1];
}
public void shiftUp(int child) {
while (child > 1 && data[child].compareTo(data[child / 2]) > 0) {
swap(child, child / 2);
child /= 2;
}
}
/**
* @param a data数组中某个元素的下角标
* @param b data数组中某个元素的下角标
* @return 哪个元素大就返回哪个的下角标
*/
private int max(int a, int b) {
if (data[a].compareTo(data[b]) < 0) {//如果data[b]大
return b;//返回b
} else {//如果data[a]大
return a;//返回a
}
}
/**
* @param a data数组中某个元素的下角标
* @param b data数组中某个元素的下角标
* @param c data数组中某个元素的下角标
* @return 哪个元素大就返回哪个的下角标
*/
private int max(int a, int b, int c) {
int biggest = max(a, b);
biggest = max(biggest, c);
return biggest;
}
public void shiftDown(int father) {
while (true) {
int lchild = father * 2;
int rchild = father * 2 + 1;
int newFather = father;//这里赋不赋值无所谓，如果把下面这个return改成break,那就必须赋值了
if (lchild > size) {//如果没有左、右孩子
return;
} else if (rchild > size) {//如果没有右孩子
newFather = max(father, lchild);
} else {//如果有左、右孩子
newFather = max(father, lchild, rchild);
}
if (newFather == father) {//如果原父结点就是三者最大，则不用继续整理堆了
return;
} else {//父节点不是最大，则把大的孩子交换上来，然后继续往下堆调整，直到满足大根堆为止
swap(newFather, father);
father = newFather;//相当于继续shiftDown(newFather)。假如newFather原来是father的左孩子，那就相当于shiftDown(2*father)
}
}
}
public static <T extends Comparable<? super T>> void sort(T[] arr) {
int len = arr.length;
MaxHeap<T> maxHeap = new MaxHeap<>(arr);
for (int i = len - 1; i >= 0; i--) {
arr[i] = maxHeap.popMax();
}
}
public static void printArr(Object[] arr) {
for (Object o : arr) {
System.out.print(o);
System.out.print("\t");
}
System.out.println();
}
public static void main(String args[]) {
Integer[] arr = {3, 5, 1, 7, 2, 9, 8, 0, 4, 6};
printArr(arr);//3 5 1 7 2 9 8 0 4 6
sort(arr);
printArr(arr);//0 1 2 3 4 5 6 7 8 9
}
}
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学如不及，犹恐失之
学如不及，犹恐失之
