001package algs15; 002import java.util.Arrays; 003import stdlib.*; 004 005/* ************************************************************************** 006 * Compilation: javac QuickUnionPathCompressionUF.java 007 * Execution: java QuickUnionPathCompressionUF < input.txt 008 * Dependencies: StdIn.java StdOut.java 009 * 010 * Quick-union with path compression. 011 * 012 ****************************************************************************/ 013 014public class CompressionUF implements UF { 015 private int[] id; // id[i] = parent of i 016 private int count; // number of components 017 018 // Create an empty union find data structure with N isolated sets. 019 public CompressionUF(int N) { 020 count = N; 021 id = new int[N]; 022 for (int i = 0; i < N; i++) { 023 id[i] = i; 024 } 025 } 026 027 // Return the number of disjoint sets. 028 public int count() { 029 return count; 030 } 031 032 // Are objects p and q in the same set? 033 public boolean connected(int p, int q) { 034 return find(p) == find(q); 035 } 036 037 // Return component identifier for component containing p 038 public int find(int p) { 039 int root = p; 040 while (root != id[root]) 041 root = id[root]; 042 while (id[p] != root) { 043 int newp = id[p]; 044 id[p] = root; 045 if (TestUF.SHOW_COMPRESSION_STEPS) { StdOut.format("%2d %2d> %2d%s\n", p, root, this.count(), this); toGraphviz(); } 046 p = newp; 047 } 048 return root; 049 } 050 051 // Replace sets containing p and q with their union. 052 public void union(int p, int q) { 053 int pid = find(p); // loser 054 int qid = find(q); // champion 055 if (pid == qid) return; 056 id[pid] = qid; 057 count--; 058 } 059 060 public String toString() { return Arrays.toString (id); } 061 public void toGraphviz() { GraphvizBuilder.ufToFile (id); } 062 063 public static void main(String[] args) { 064 boolean print = true; 065 StdIn.fromFile ("data/tinyUF.txt"); 066 //StdIn.fromFile ("data/mediumUF.txt"); print = false; 067 //StdIn.fromFile ("data/largeUF.txt"); print = false; 068 069 int N = StdIn.readInt(); 070 CompressionUF uf = new CompressionUF(N); 071 if (print) { uf.toGraphviz(); StdOut.println(" : " + uf); } 072 073 // read in a sequence of pairs of integers (each in the range 0 to N-1), 074 // calling find() for each pair: If the members of the pair are not already 075 // call union() and print the pair. 076 Stopwatch sw = new Stopwatch (); 077 while (!StdIn.isEmpty()) { 078 int p = StdIn.readInt(); 079 int q = StdIn.readInt(); 080 if (uf.connected(p, q)) continue; 081 uf.union(p, q); 082 if (print) { StdOut.println(p + " " + q + ": " + uf); uf.toGraphviz(); } 083 } 084 StdOut.format("CompressionUF # components: %d [%f]\n", uf.count(), sw.elapsedTime ()); 085 } 086 087}