算法（Algorithms）第4版 练习 1.5.16

Quick-find

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFQuickFind {
    
    private int[] id;//access to component id (site indexed)
    private int count;//number of components
    
    private static int cost = 0;//for plot
    
    public UFQuickFind(int n) {
        //initialize count and id
        count = n;
        
        id = new int[n];
        for(int i = 0; i < n; i++) {
            id[i] = i;
        }
        
    }
    
    public int count() {
        return count;
    }
    
    public boolean connected(int p, int q) {
        return find(p) == find(q);
    }
    
    public int find(int p) {
        cost++;//for plot
        return id[p];
    }
    
    public void union(int p, int q) {
        
        int pID = find(p);
        int qID = find(q);
        
        //do nothing if p and q are already
        //in the same component
        if(pID == qID) 
            return;
        
        //rename p's component to q's name
        for(int i = 0; i < id.length; i++) {
            if(id[i] == pID) {
                id[i] = qID;
                cost++;//for plot
            }
            cost++;//for plot
        }
        count--;
        
    }
    
    @Override
    public String toString() {
        String s = "";
        
        for(int i = 0; i < id.length; i++) {
            s += id[i] + " ";
        }
        s += "
" + count + " components";
        
        return s;
    }
    
    //for plot
    private static void initStdDraw() {
        StdDraw.setXscale(0, 900);
        StdDraw.setYscale(0, 1300);
        StdDraw.setPenRadius(0.002);
        StdDraw.textLeft(1, 625, "625");
    }
    
    //for plot
    private static void plot(int i, int cost, int totalcost) {
        
        double average = (totalcost * 1.0) / i;
        
        StdDraw.setPenColor(StdDraw.BLACK);
        StdDraw.point(i, cost);
        StdDraw.setPenColor(StdDraw.RED);
        StdDraw.point(i, average);
    }

    public static void main(String[] args) {
        
        //initialize N components
        int N = StdIn.readInt();
        UFQuickFind uf = new UFQuickFind(N);
//        StdOut.println(uf);
        
        //total cost for plot
        int totalcost = 0;
        int i = 0;//ith connection processed
        initStdDraw();
        
        while(!StdIn.isEmpty()) {
            
            cost = 0;//initialize for every inputs pair, for plot
            
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            
            if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");
                
                totalcost += cost;//compute total cost, for plot
                i++;
                plot(i, cost, totalcost);
                
                continue;
            }
            
            uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);
            
            totalcost += cost;//compute total cost, for plot
            i++;
            plot(i,cost,totalcost);
        }
        
    }

}

Quick-union

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFQuickUnion {

    private int[] id;//save the site's parent link(site indexed)
    private int count;//number of components
    
    private static int cost = 0;//for plot
    
    public UFQuickUnion(int n) {
        
        count = n;
        
        id = new int[n];
        for(int i = 0; i < n; i++)
            id[i] = i;
        
    }
    
    public int count() {
        return count;
    }
    
    public boolean connected(int p, int q) {
        return find(p) == find(q);
    }
    
    public int find(int p) {
        
        //find root
        //id[p] save the parent of p
        while(p != id[p]) {
            p = id[p];
            cost += 2;//for plot
        }
        cost++;//for plot
        
        return p;
    }
    
    public void union(int p, int q) {
        
        int pRoot = find(p);//find pRoot
        int qRoot = find(q);//find qRoot
        
        if(pRoot == qRoot)
            return;
        
        id[pRoot] = qRoot;
        cost++;//for plot
        count--;
    }
    
    @Override
    public String toString() {
        String s = "";
        
        for(int i = 0; i < id.length; i++) {
            s += id[i] + " ";
        }
        s += "
" + count + " components";
        
        return s;
    }
    
    
    //for plot
    private static void initStdDraw() {
        StdDraw.setXscale(0, 900);
        StdDraw.setYscale(0, 1300);
        StdDraw.setPenRadius(0.002);
        StdDraw.textLeft(1, 650, "625");
    }
    
    //for plot
    private static void plot(int i, int cost, int totalcost) {
        
        double average = (totalcost * 1.0) / i;
        
        StdDraw.setPenColor(StdDraw.BLACK);
        StdDraw.point(i, cost);
        StdDraw.setPenColor(StdDraw.RED);
        StdDraw.point(i, average);
    }
        
    public static void main(String[] args) {
        
        //initialize N components
        int N = StdIn.readInt();
        UFQuickUnion uf = new UFQuickUnion(N);
//        StdOut.println(uf);
        
        //total cost for plot
        int totalcost = 0;
        int i = 0;//ith connection processed
        initStdDraw();
        
        while(!StdIn.isEmpty()) {
            
            cost = 0;//initialize for every inputs pair, for plot
            
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            
            if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");
                
                totalcost += cost;//compute total cost, for plot
                i++;
                plot(i, cost, totalcost);
                
                continue;
            }
            
            uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);
            
            totalcost += cost;//compute total cost, for plot
            i++;
            plot(i, cost, totalcost);
        }
        
    }

}

Weighted-quick union

package com.qiusongde;

import edu.princeton.cs.algs4.StdDraw;
import edu.princeton.cs.algs4.StdIn;
import edu.princeton.cs.algs4.StdOut;

public class UFWeightedQuickUnion {

    private int[] id;//parent link(site indexed)
    private int[] treesize;//size of component for roots(site indexed)
    private int count;//number of components
    
    private static int cost = 0;//for plot
    
    public UFWeightedQuickUnion(int N) {
        
        count = N;
        
        id = new int[N];
        for(int i = 0; i < N; i++) 
            id[i] = i;
        
        treesize = new int[N];
        for(int i = 0; i < N; i++)
            treesize[i] = 1;
        
    }
    
    public int count() {
        return count;
    }
    
    public boolean connected(int p, int q) {
        return find(p) == find(q);
    }
    
    public int find(int p) {
        
        while(p != id[p]) {
            p = id[p];
            cost += 2;//for plot
        }
        cost++;//for plot
        
        return p;
        
    }
    
    public void union(int p, int q) {
        
        int pRoot = find(p);
        int qRoot = find(q);
        
        if(pRoot == qRoot)
            return;
        
        //make smaller root point to larger one
        if(treesize[pRoot] < treesize[qRoot]) {
            id[pRoot] = qRoot;
            treesize[qRoot] += treesize[pRoot];
            cost += 5;//for plot
        } else {
            id[qRoot] = pRoot;
            treesize[pRoot] += treesize[qRoot]; 
            cost += 5;//for plot
        }
        
        count--;
        
    }
    
    @Override
    public String toString() {
        String s = "";
        
        for(int i = 0; i < id.length; i++) {
            s += id[i] + " ";
        }
        s += "
";
        
        for(int i = 0; i < treesize.length; i++) {
            s += treesize[i] + " ";
        }
        s += "
" + count + " components";
        
        return s;
    }
    
    //for plot
      private static void initStdDraw() {
          StdDraw.setXscale(0, 900);
          StdDraw.setYscale(0, 1300);
          StdDraw.setPenRadius(0.002);
          StdDraw.textLeft(1, 625, "625");
      }
      
      //for plot
      private static void plot(int i, int cost, int totalcost) {
          
          double average = (totalcost * 1.0) / i;
          
          StdDraw.setPenColor(StdDraw.BLACK);
          StdDraw.point(i, cost);
          StdDraw.setPenColor(StdDraw.RED);
          StdDraw.point(i, average);
      }
    
    public static void main(String[] args) {
        
        //initialize N components
        int N = StdIn.readInt();
        UFWeightedQuickUnion uf = new UFWeightedQuickUnion(N);
//        StdOut.println(uf);
        
        //total cost for plot
        int totalcost = 0;
        int i = 0;//ith connection processed
        initStdDraw();
              
        while(!StdIn.isEmpty()) {
            
            cost = 0;//initialize for every inputs pair, for plot
            
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            
            if(uf.connected(p, q)) {//ignore if connected
//                StdOut.println(p + " " + q + " is connected");
                
                totalcost += cost;//compute total cost, for plot
                i++;
                plot(i, cost, totalcost);
                
                continue;
            }
            
            uf.union(p, q);//connect p and q
//            StdOut.println(p + " " + q);
//            StdOut.println(uf);
            
            totalcost += cost;//compute total cost, for plot
            i++;
            plot(i, cost, totalcost);
        }
        
    }
    
}