dataStructure@ Implementation of minimal heap
Posted 流白
tags:
篇首语:本文由小常识网(cha138.com)小编为大家整理,主要介绍了dataStructure@ Implementation of minimal heap相关的知识,希望对你有一定的参考价值。
A binary heap is a heap data structure created using a binary tree.
binary tree has two rules -
- Binary Heap has to be complete binary tree at all levels except the last level. This is called shape property.
- All nodes are either greater than equal to (Max-Heap) or less than equal to (Min-Heap) to each of its child nodes. This is called heap property.
Implementation:
- Use array to store the data.
- Start storing from index 1, not 0.
- For any given node at position i:
- Its Left Child is at [2*i] if available.
- Its Right Child is at [2*i+1] if available.
- Its Parent Node is at [i/2]if available.
Heap Majorly has 3 operations -
- Insert Operation
- Delete Operation
- Extract-Min (OR Extract-Max)
Insert Operation:
- Add the element at the bottom leaf of the Heap.
- Perform the Bubble-Up operation.
- All Insert Operations must perform the bubble-up operation(it is also called as up-heap, percolate-up, sift-up, trickle-up, heapify-up, or cascade-up)
Bubble-up Operation:
- If inserted element is smaller than its parent node in case of Min-Heap OR greater than its parent node in case of Max-Heap, swap the element with its parent.
- Keep repeating the above step, if node reaches its correct position, STOP.
Extract-Min OR Extract-Max Operation:
- Take out the element from the root.( it will be minimum in case of Min-Heap and maximum in case of Max-Heap).
- Take out the last element from the last level from the heap and replace the root with the element.
- Perform Sink-Down
- All delete operation must perform Sink-Down Operation ( also known as bubble-down, percolate-down, sift-down, trickle down, heapify-down, cascade-down).
Sink-Down Operation:
- If replaced element is greater than any of its child node in case of Min-Heap OR smaller than any if its child node in case of Max-Heap, swap the element with its smallest child(Min-Heap) or with its greatest child(Max-Heap).
- Keep repeating the above step, if node reaches its correct position, STOP.
Delete Operation:
- Find the index for the element to be deleted.
- Take out the last element from the last level from the heap and replace the index with this element .
- Perform Sink-Down
Time and Space Complexity:
Space | O(n) |
Search | O(n) |
Insert | O(log n) |
Delete | O(log n) |
package data_structure_testing; import java.util.ArrayList; import java.util.HashSet; public class MinHeap { public ArrayList<Integer> minheap = null; public MinHeap() { this.minheap = new ArrayList<Integer> (); this.minheap.add(Integer.MIN_VALUE); /** * ------------------------------------------------------------------------- * Integer.MIN_VALUE | | | | | | | | | | | | | | | | | | | * ------------------------------------------------------------------------- */ } public void swap(int i, int j) { if(i == j) return; int tmp = minheap.get(i); minheap.set(i, minheap.get(j)); minheap.set(j, tmp); } public int getSize() { return minheap.size(); } public int parent(int i) { return i/2; } public int leftChild(int i) { return i*2; } public int rightChild(int i) { return i*2 + 1; } public void offer(int x) { minheap.add(x); int position = minheap.size() - 1; bubbleUp(position); } public void bubbleUp(int position) { int pa = parent(position); if(pa != 0 && minheap.get(position) < minheap.get(pa)) { swap(position, pa); bubbleUp(pa); } } public int peek() { if(getSize() == 1) { System.out.println("the min heap is empty!"); return minheap.get(0); } else{ return minheap.get(1); } } public void pushDown(int i) { int min_position = i, min_value = minheap.get(i); int lc = leftChild(i), rc = lc + 1; if(lc >= getSize()) { return; } if(lc < getSize()) { if(minheap.get(lc) < min_value) { min_position = lc; min_value = minheap.get(lc); } if(rc < getSize() && minheap.get(rc) < min_value) { min_position = rc; } } swap(min_position, i); if(min_position != i) { pushDown(min_position); } } public int poll() { if(getSize() == 1) { System.out.println("since the min heap is empty, so we cannot poll any element from it!"); return minheap.get(0); } int top = minheap.get(1); swap(1, getSize()-1); minheap.remove(getSize()-1); if(getSize() > 1) { pushDown(1); } return top; } public static void main(String[] args) { MinHeap minheap = new MinHeap(); minheap.offer(5); minheap.offer(4); minheap.offer(2); minheap.offer(4); minheap.offer(3); System.out.println(minheap.poll()); System.out.println(minheap.poll()); System.out.println(minheap.poll()); System.out.println(minheap.poll()); System.out.println(minheap.poll()); System.out.println(minheap.poll()); } }
以上是关于dataStructure@ Implementation of minimal heap的主要内容,如果未能解决你的问题,请参考以下文章