322 Multiway merge priority queue client

Posted 2020-11-10 w-j-c

import edu.princeton.cs.algs4.*;

public class Multiway
{
    public static void merge(In[] streams)
    {
        int N = streams.length;
        IndexMinPQ<String> pq = new IndexMinPQ<String>(N);
        
        for(int i = 0; i < N; i++)
        {
            if(!streams[i].isEmpty())
                pq.insert(i,streams[i].readString());
        }
        
        while(!pq.isEmpty())//也就是这里的pq大多数时间一直保持三个元素,最后会因为没有输入而减少元素个数
        {
            StdOut.println(pq.minKey());//IndexMinPQ没有min方法,只有minKey(),应该是书本错误
            int i = pq.delMin();
            if(!streams[i].isEmpty())//若删除的那一行streams非空,就再插入一个该行的元素
                pq.insert(i,streams[i].readString());
        }
    }
    
    public static void main(String[] args)
    {
        //输入的本来就是有序的了
        int N = args.length;
        In[] streams = new In[N];
        for(int i = 0; i < N; i++)
            streams[i] = new In(args[i]);
        merge(streams);
    }
}