算法第四版 用eclipse实现书中UnionFind例子

一 安装环境

直接下载algs4.exe

下载完成后C:Userszle 下面会有algs4 文件夹

原文：

Our installer downloads, installs, and configures the Java programming environment you will be using, including Java SE 7, DrJava, the textbook libraries, and the Command Prompt.

• Log in to the user account in which you will be programming. Your account must have Administrator privileges and you must be connected to the Internet. 
• Download algs4.exe and double-click it to perform the installation. If you receive a User Account Control alert before the installation, click Yes or Allow; if you receive a Program Compatibility Assistant alert after the installation, click This program installed correctly. 
• If the installation succeeds, you will see the following:
  • A Command Prompt windows containing approximately this execution log 
  • A Standard Drawing window containing a blue bullseye and textbook graphic.

  Note that the installation can take several minutes or longer if you have a slow internet connection. 

• Delete algs4.exe.

 二 将这个文件夹复制到eclipse工作环境下

3 在eclipse中设置cmd环境

选择 External tools configrations

Name 名字随便取我的是UF1.5

Location 是cmd的目录

working director 默认的工作目录

三 编写程序并运行

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

public class WeightedQuickUnionUF {
    private int[] id;    // id[i] = parent of i
    private int[] sz;    // sz[i] = number of objects in subtree rooted at i
    private int count;   // number of components

    // Create an empty union find data structure with N isolated sets.
    public WeightedQuickUnionUF(int N) {
        count = N;
        id = new int[N];
        sz = new int[N];
        for (int i = 0; i < N; i++) {
            id[i] = i;
            sz[i] = 1;
        }
    }

    // Return the number of disjoint sets.
    public int count() {
        return count;
    }

    // Return component identifier for component containing p
    public int find(int p) {
        while (p != id[p])
            p = id[p];
        return p;
    }

   // Are objects p and q in the same set?
    public boolean connected(int p, int q) {
        return find(p) == find(q);
    }

  
   // Replace sets containing p and q with their union.
    public void union(int p, int q) {
        int i = find(p);
        int j = find(q);
        if (i == j) return;

        // make smaller root point to larger one
        if   (sz[i] < sz[j]) { id[i] = j; sz[j] += sz[i]; }
        else                 { id[j] = i; sz[i] += sz[j]; }
        count--;
    }


    public static void main(String[] args) {
        int N = StdIn.readInt();
        WeightedQuickUnionUF uf = new WeightedQuickUnionUF(N);

        // read in a sequence of pairs of integers (each in the range 0 to N-1),
         // calling find() for each pair: If the members of the pair are not already
        // call union() and print the pair.
        while (!StdIn.isEmpty()) {
            int p = StdIn.readInt();
            int q = StdIn.readInt();
            if (uf.connected(p, q)) continue;
            uf.union(p, q);
            StdOut.println(p + " " + q);
        }
        StdOut.println("# components: " + uf.count());
    }

}

点击刚刚创建的UF1.5

在console可以看到cmd

进入bin 目录下 因为.class文件在bin目录下

 在命令框内输入

折磨了好久终于搞好啦！

参考：http://algs4.cs.princeton.edu/windows/