二叉堆優先佇列

壹頁書發表於2016-09-22
佇列


  1. public class MaxPQ <Key extends Comparable<Key>> {
  2.     private Key[] pq;
  3.     private int N=0;
  4.     public MaxPQ(int maxN){
  5.         pq=(Key[])new Comparable[maxN+1];
  6.     }

  8.     public boolean isEmpty(){
  9.         return N==0;
  10.     }

  12.     public int size(){
  13.         return N;
  14.     }

  16.     public void insert(Key v){
  17.         pq[++N]=v;
  18.         swim(N);
  19.     }

  21.     private void swim(int k) {
  22.         while(k>1 && less(k/2,k)){
  23.             exch(k/2,k);
  24.             k=k/2;
  25.         }
  26.     }

  28.     private boolean less(int i, int j) {
  29.         return pq[i].compareTo(pq[j])<0;
  30.     }

  32.     public Key delMax(){
  33.         Key max=pq[1] ;
  34.         exch(1,N--);
  35.         pq[N+1]=null;
  36.         sink(1);
  37.         return max;
  38.     }

  40.     private void sink(int k) {
  41.         while(2*k<=N){
  42.             int j=2*k;
  43.             if(j<N && less(j,j+1))
  44.                 j++;
  45.             if(!less(k,j))
  46.                 break;
  47.             exch(k,j);
  48.             k=j;
  49.         }
  50.     }

  52.     private void exch(int i, int j) {
  53.         Key t=pq[i];
  54.         pq[i]=pq[j];
  55.         pq[j]=t;
  56.     }

  58.     public static void main(String[] args){
  59.         Integer[] data={100,20,21,28,22,26,80,33,3,2,9,8,7,10,77,66,99,96,91,94};

  61.         MaxPQ<Integer> pq=new MaxPQ<>(data.length);
  62.         for(int i=0;i<data.length;i++){
  63.             pq.insert(data[i]);
  64.         }
  65.         while(!pq.isEmpty()){
  66.             System.out.println(pq.delMax());
  67.         }
  68.     }
  69. }

來自 “ ITPUB部落格 ” ，連結：http://blog.itpub.net/29254281/viewspace-2125325/，如需轉載，請註明出處，否則將追究法律責任。

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