@ -0,0 +1,67 @@
|
||||
/**
|
||||
* File: my_heap.java
|
||||
* Created Time: 2023-01-07
|
||||
* Author: Krahets (krahets@163.com)
|
||||
*/
|
||||
|
||||
package chapter_heap;
|
||||
|
||||
import include.*;
|
||||
import java.util.*;
|
||||
|
||||
|
||||
public class heap {
|
||||
public static void testPush(Queue<Integer> heap, int val) {
|
||||
heap.add(val); // 元素入堆
|
||||
System.out.format("\n元素 %d 入堆后\n", val);
|
||||
PrintUtil.printHeap(heap);
|
||||
}
|
||||
|
||||
public static void testPoll(Queue<Integer> heap) {
|
||||
int val = heap.poll(); // 堆顶元素出堆
|
||||
System.out.format("\n堆顶元素 %d 出堆后\n", val);
|
||||
PrintUtil.printHeap(heap);
|
||||
}
|
||||
|
||||
public static void main(String[] args) {
|
||||
/* 初始化堆 */
|
||||
// 初始化小顶堆
|
||||
Queue<Integer> minHeap = new PriorityQueue<>();
|
||||
// 初始化大顶堆(使用 lambda 表达式修改 Comparator 即可)
|
||||
Queue<Integer> maxHeap = new PriorityQueue<>((a, b) -> { return b - a; });
|
||||
|
||||
System.out.println("\n以下测试样例为大顶堆");
|
||||
|
||||
/* 元素入堆 */
|
||||
testPush(maxHeap, 1);
|
||||
testPush(maxHeap, 3);
|
||||
testPush(maxHeap, 2);
|
||||
testPush(maxHeap, 5);
|
||||
testPush(maxHeap, 4);
|
||||
|
||||
/* 获取堆顶元素 */
|
||||
int peek = maxHeap.peek();
|
||||
System.out.format("\n堆顶元素为 %d\n", peek);
|
||||
|
||||
/* 堆顶元素出堆 */
|
||||
testPoll(maxHeap);
|
||||
testPoll(maxHeap);
|
||||
testPoll(maxHeap);
|
||||
testPoll(maxHeap);
|
||||
testPoll(maxHeap);
|
||||
|
||||
/* 获取堆大小 */
|
||||
int size = maxHeap.size();
|
||||
System.out.format("\n堆元素数量为 %d\n", size);
|
||||
|
||||
/* 判断堆是否为空 */
|
||||
boolean isEmpty = maxHeap.isEmpty();
|
||||
System.out.format("\n堆是否为空 %b\n", isEmpty);
|
||||
|
||||
/* 输入列表并建堆 */
|
||||
// 时间复杂度为 O(n) ,而非 O(nlogn)
|
||||
minHeap = new PriorityQueue<>(Arrays.asList(1, 3, 2, 5, 4));
|
||||
System.out.println("\n输入列表并建立小顶堆后");
|
||||
PrintUtil.printHeap(minHeap);
|
||||
}
|
||||
}
|
@ -0,0 +1,177 @@
|
||||
/**
|
||||
* File: my_heap.java
|
||||
* Created Time: 2023-01-07
|
||||
* Author: Krahets (krahets@163.com)
|
||||
*/
|
||||
|
||||
package chapter_heap;
|
||||
|
||||
import include.*;
|
||||
import java.util.*;
|
||||
|
||||
class MaxHeap {
|
||||
// 使用列表而非数组,这样无需考虑扩容问题
|
||||
private List<Integer> maxHeap;
|
||||
|
||||
/* 构造函数,建立空堆 */
|
||||
public MaxHeap() {
|
||||
maxHeap = new ArrayList<>();
|
||||
}
|
||||
|
||||
/* 构造函数,根据输入列表建堆 */
|
||||
public MaxHeap(List<Integer> nums) {
|
||||
// 所有元素入堆
|
||||
maxHeap = new ArrayList<>(nums);
|
||||
// 堆化除叶结点以外的其他所有结点
|
||||
for (int i = parent(size() - 1); i >= 0; i--) {
|
||||
siftDown(i);
|
||||
}
|
||||
}
|
||||
|
||||
/* 获取左子结点索引 */
|
||||
private int left(int i) {
|
||||
return 2 * i + 1;
|
||||
}
|
||||
|
||||
/* 获取右子结点索引 */
|
||||
private int right(int i) {
|
||||
return 2 * i + 2;
|
||||
}
|
||||
|
||||
/* 获取父结点索引 */
|
||||
private int parent(int i) {
|
||||
return (i - 1) / 2; // 向下整除
|
||||
}
|
||||
|
||||
/* 交换元素 */
|
||||
private void swap(int i, int j) {
|
||||
int a = maxHeap.get(i),
|
||||
b = maxHeap.get(j),
|
||||
tmp = a;
|
||||
maxHeap.set(i, b);
|
||||
maxHeap.set(j, tmp);
|
||||
}
|
||||
|
||||
/* 获取堆大小 */
|
||||
public int size() {
|
||||
return maxHeap.size();
|
||||
}
|
||||
|
||||
/* 判断堆是否为空 */
|
||||
public boolean isEmpty() {
|
||||
return size() == 0;
|
||||
}
|
||||
|
||||
/* 访问堆顶元素 */
|
||||
public int peek() {
|
||||
return maxHeap.get(0);
|
||||
}
|
||||
|
||||
/* 元素入堆 */
|
||||
public void push(int val) {
|
||||
// 添加结点
|
||||
maxHeap.add(val);
|
||||
// 从底至顶堆化
|
||||
siftUp(size() - 1);
|
||||
}
|
||||
|
||||
/* 从结点 i 开始,从底至顶堆化 */
|
||||
private void siftUp(int i) {
|
||||
while (true) {
|
||||
// 获取结点 i 的父结点
|
||||
int p = parent(i);
|
||||
// 当“越过根结点”或“结点无需修复”时,结束堆化
|
||||
if (p < 0 || maxHeap.get(i) <= maxHeap.get(p))
|
||||
break;
|
||||
// 交换两结点
|
||||
swap(i, p);
|
||||
// 循环向上堆化
|
||||
i = p;
|
||||
}
|
||||
}
|
||||
|
||||
/* 元素出堆 */
|
||||
public int poll() {
|
||||
// 判空处理
|
||||
if (isEmpty())
|
||||
throw new EmptyStackException();
|
||||
// 交换根结点与最右叶结点(即交换首元素与尾元素)
|
||||
swap(0, size() - 1);
|
||||
// 删除结点
|
||||
int val = maxHeap.remove(size() - 1);
|
||||
// 从顶至底堆化
|
||||
siftDown(0);
|
||||
// 返回堆顶元素
|
||||
return val;
|
||||
}
|
||||
|
||||
/* 从结点 i 开始,从顶至底堆化 */
|
||||
private void siftDown(int i) {
|
||||
while (true) {
|
||||
// 判断结点 i, l, r 中值最大的结点,记为 ma
|
||||
int l = left(i), r = right(i), ma = i;
|
||||
if (l < size() && maxHeap.get(l) > maxHeap.get(ma))
|
||||
ma = l;
|
||||
if (r < size() && maxHeap.get(r) > maxHeap.get(ma))
|
||||
ma = r;
|
||||
// 若结点 i 最大或索引 l, r 越界,则无需继续堆化,跳出
|
||||
if (ma == i) break;
|
||||
// 交换两结点
|
||||
swap(i, ma);
|
||||
// 循环向下堆化
|
||||
i = ma;
|
||||
}
|
||||
}
|
||||
|
||||
/* 打印堆(二叉树) */
|
||||
public void print() {
|
||||
Queue<Integer> queue = new PriorityQueue<>((a, b) -> { return b - a; });
|
||||
queue.addAll(maxHeap);
|
||||
PrintUtil.printHeap(queue);
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
public class my_heap {
|
||||
public static void testPush(MaxHeap maxHeap, int val) {
|
||||
maxHeap.push(val); // 元素入堆
|
||||
System.out.format("\n添加元素 %d 后\n", val);
|
||||
maxHeap.print();
|
||||
}
|
||||
|
||||
public static void testPoll(MaxHeap maxHeap) {
|
||||
int val = maxHeap.poll(); // 堆顶元素出堆
|
||||
System.out.format("\n出堆元素为 %d\n", val);
|
||||
maxHeap.print();
|
||||
}
|
||||
|
||||
public static void main(String[] args) {
|
||||
/* 初始化大顶堆 */
|
||||
MaxHeap maxHeap = new MaxHeap(Arrays.asList(9, 8, 6, 6, 7, 5, 2, 1, 4, 3, 6, 2));
|
||||
System.out.println("\n输入列表并建堆后");
|
||||
maxHeap.print();
|
||||
|
||||
/* 获取堆顶元素 */
|
||||
int peek = maxHeap.peek();
|
||||
System.out.format("\n堆顶元素为 %d\n", peek);
|
||||
|
||||
/* 元素入堆 */
|
||||
int val = 7;
|
||||
maxHeap.push(val);
|
||||
System.out.format("\n元素 %d 入堆后\n", val);
|
||||
maxHeap.print();
|
||||
|
||||
/* 堆顶元素出堆 */
|
||||
peek = maxHeap.poll();
|
||||
System.out.format("\n堆顶元素 %d 出堆后\n", peek);
|
||||
maxHeap.print();
|
||||
|
||||
/* 获取堆大小 */
|
||||
int size = maxHeap.size();
|
||||
System.out.format("\n堆元素数量为 %d\n", size);
|
||||
|
||||
/* 判断堆是否为空 */
|
||||
boolean isEmpty = maxHeap.isEmpty();
|
||||
System.out.format("\n堆是否为空 %b\n", isEmpty);
|
||||
}
|
||||
}
|
After Width: | Height: | Size: 69 KiB |
After Width: | Height: | Size: 89 KiB |
After Width: | Height: | Size: 66 KiB |
After Width: | Height: | Size: 69 KiB |
After Width: | Height: | Size: 81 KiB |
After Width: | Height: | Size: 89 KiB |
After Width: | Height: | Size: 85 KiB |
After Width: | Height: | Size: 94 KiB |
After Width: | Height: | Size: 87 KiB |
After Width: | Height: | Size: 96 KiB |
After Width: | Height: | Size: 69 KiB |
After Width: | Height: | Size: 66 KiB |
After Width: | Height: | Size: 81 KiB |
After Width: | Height: | Size: 84 KiB |
After Width: | Height: | Size: 85 KiB |
After Width: | Height: | Size: 85 KiB |
After Width: | Height: | Size: 64 KiB |
After Width: | Height: | Size: 80 KiB |
After Width: | Height: | Size: 113 KiB |