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68 lines
2.0 KiB
68 lines
2.0 KiB
/**
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* File: heap.java
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* Created Time: 2023-01-07
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* Author: Krahets (krahets@163.com)
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*/
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package chapter_heap;
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import include.*;
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import java.util.*;
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public class heap {
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public static void testPush(Queue<Integer> heap, int val) {
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heap.add(val); // 元素入堆
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System.out.format("\n元素 %d 入堆后\n", val);
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PrintUtil.printHeap(heap);
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}
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public static void testPoll(Queue<Integer> heap) {
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int val = heap.poll(); // 堆顶元素出堆
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System.out.format("\n堆顶元素 %d 出堆后\n", val);
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PrintUtil.printHeap(heap);
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}
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public static void main(String[] args) {
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/* 初始化堆 */
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// 初始化小顶堆
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Queue<Integer> minHeap = new PriorityQueue<>();
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// 初始化大顶堆（使用 lambda 表达式修改 Comparator 即可）
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Queue<Integer> maxHeap = new PriorityQueue<>((a, b) -> { return b - a; });
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System.out.println("\n以下测试样例为大顶堆");
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/* 元素入堆 */
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testPush(maxHeap, 1);
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testPush(maxHeap, 3);
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testPush(maxHeap, 2);
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testPush(maxHeap, 5);
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testPush(maxHeap, 4);
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/* 获取堆顶元素 */
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int peek = maxHeap.peek();
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System.out.format("\n堆顶元素为 %d\n", peek);
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/* 堆顶元素出堆 */
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testPoll(maxHeap);
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testPoll(maxHeap);
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testPoll(maxHeap);
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testPoll(maxHeap);
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testPoll(maxHeap);
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/* 获取堆大小 */
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int size = maxHeap.size();
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System.out.format("\n堆元素数量为 %d\n", size);
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/* 判断堆是否为空 */
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boolean isEmpty = maxHeap.isEmpty();
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System.out.format("\n堆是否为空 %b\n", isEmpty);
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/* 输入列表并建堆 */
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// 时间复杂度为 O(n) ，而非 O(nlogn)
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minHeap = new PriorityQueue<>(Arrays.asList(1, 3, 2, 5, 4));
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System.out.println("\n输入列表并建立小顶堆后");
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PrintUtil.printHeap(minHeap);
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}
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}
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