001package algs24; 002import stdlib.*; 003/* *********************************************************************** 004 * Compilation: javac Multiway.java 005 * Execution: java Multiway input1.txt input2.txt input3.txt ... 006 * Dependencies: IndexMinPQ.java In.java StdOut.java 007 * 008 * Merges together the sorted input stream given as command-line arguments 009 * into a single sorted output stream on standard output. 010 * 011 * % more m1.txt 012 * A B C F G I I Z 013 * 014 * % more m2.txt 015 * B D H P Q Q 016 * 017 * % more m3.txt 018 * A B E F J N 019 * 020 * % java Multiway m1.txt m2.txt m3.txt 021 * A A B B B C D E F F G H I I J N P Q Q Z 022 * 023 *************************************************************************/ 024 025public class Multiway { 026 027 public static void merge(In[] streams) { 028 int N = streams.length; 029 IndexMinPQ<String> pq = new IndexMinPQ<>(N); 030 031 // read the first String from each stream 032 for (int i = 0; i < N; i++) 033 if (!streams[i].isEmpty()) 034 pq.insert(i, streams[i].readString()); 035 036 // Extract and print min and read next from its stream. 037 while (!pq.isEmpty()) { 038 StdOut.print(pq.minKey() + " "); 039 int i = pq.delMin(); 040 if (!streams[i].isEmpty()) 041 pq.insert(i, streams[i].readString()); 042 } 043 StdOut.println(); 044 } 045 046 public static void main(String[] args) { 047 args = new String[] { "data/m1.txt", "data/m2.txt", "data/m3.txt" }; 048 int N = args.length; 049 In[] streams = new In[N]; 050 for (int i = 0; i < N; i++) 051 streams[i] = new In(args[i]); 052 merge(streams); 053 } 054}