? 书中第三章部分程序，加上自己补充的代码，包含双向索引表、文建索引、稀疏向量类型
● 双向索引表
1 package package01;
2
3 import edu.princeton.cs.algs4.ST;
4 import edu.princeton.cs.algs4.Queue;
5 import edu.princeton.cs.algs4.In;
6 import edu.princeton.cs.algs4.StdIn;
7 import edu.princeton.cs.algs4.StdOut;
8
9 public class class01
10 {
11 private class01() {}
12
13 public static void main(String[] args)
14 {
15 String filename = args[0];
16 String separator = args[1];
17 In in = new In(filename);
18
19 ST<String, Queue<String>> st = new ST<String, Queue<String>>();
20 ST<String, Queue<String>> ts = new ST<String, Queue<String>>(); // 反向索引
21
22 for(;in.hasNextLine();)
23 {
24 String line = in.readLine();
25 String[] fields = line.split(separator);
26 String key = fields[0];
27 for (int i = 1; i < fields.length; i++) // 一个 key 对应多个值，分别存放，以后可以根据值反向查找键
28 {
29 String val = fields[i];
30 if (!st.contains(key))
31 st.put(key, new Queue<String>());
32 if (!ts.contains(val))
33 ts.put(val, new Queue<String>());
34 st.get(key).enqueue(val);
35 ts.get(val).enqueue(key);
36 }
37 }
38 StdOut.println("Done indexing");
39 for(;!StdIn.isEmpty();) // 交互式查找，可以正向也可以反向
40 {
41 String query = StdIn.readLine();
42 if (st.contains(query))
43 {
44 for (String vals : st.get(query))
45 StdOut.println(" " + vals);
46 }
47 if (ts.contains(query))
48 {
49 for (String keys : ts.get(query))
50 StdOut.println(" " + keys);
51 }
52 }
53 }
54 }
● 文件索引
1 package package01;
2
3 import java.io.File;
4 import edu.princeton.cs.algs4.SET;
5 import edu.princeton.cs.algs4.ST;
6 import edu.princeton.cs.algs4.In;
7 import edu.princeton.cs.algs4.StdIn;
8 import edu.princeton.cs.algs4.StdOut;
9
10 public class class01
11 {
12 private class01() {}
13
14 public static void main(String[] args)
15 {
16 ST<String, SET<File>> st = new ST<String, SET<File>>();
17 StdOut.println("Indexing files");
18 for (String filename : args)
19 {
20 StdOut.println(" " + filename);
21 File file = new File(filename);
22 for(In in = new In(file);!in.isEmpty();)
23 {
24 String word = in.readString();
25 if (!st.contains(word))
26 st.put(word, new SET<File>());
27 SET<File> set = st.get(word);
28 set.add(file);
29 }
30 }
31 for(;StdIn.isEmpty();) // 交互式查找包含特定单词的文件
32 {
33 String query = StdIn.readString();
34 if (st.contains(query))
35 {
36 SET<File> set = st.get(query);
37 for (File file : set)
38 StdOut.println(" " + file.getName());
39 }
40 }
41 }
42 }
● 稀疏向量类型
1 package package01;
2
3 import edu.princeton.cs.algs4.ST;
4 import edu.princeton.cs.algs4.StdOut;
5
6 public class class01
7 {
8 private int d; // 向量维数
9 private ST<Integer, Double> st; // 向量 index - value 对
10
11 public class01(int d)
12 {
13 this.d = d;
14 this.st = new ST<Integer, Double>();
15 }
16
17 public void put(int i, double value)
18 {
19 if (i < 0 || i >= d)
20 throw new IllegalArgumentException("\n<put> i < 0 || i >= d.\n");
21 if (value == 0.0)
22 st.delete(i);
23 else
24 st.put(i, value);
25 }
26
27 public double get(int i)
28 {
29 if (i < 0 || i >= d)
30 throw new IllegalArgumentException("\n<get> i < 0 || i >= d.\n");
31 return (st.contains(i)) ? st.get(i) : 0.0;
32 }
33
34 public int nnz()
35 {
36 return st.size();
37 }
38
39 @Deprecated
40 public int dimension() { return d; }
41
42 public double dot(class01 that)
43 {
44 if (this.d != that.d)
45 throw new IllegalArgumentException("\n<dot> dimension disagree.\n");
46 double sum = 0.0;
47 if (this.st.size() <= that.st.size()) // 遍历元素较少的向量，去元素较多的向量中查找
48 {
49 for (int i : this.st.keys())
50 {
51 if (that.st.contains(i))
52 sum += this.get(i) * that.get(i);
53 }
54 }
55 else
56 {
57 for (int i : that.st.keys())
58 {
59 if (this.st.contains(i))
60 sum += this.get(i) * that.get(i);
61 }
62 }
63 return sum;
64 }
65
66 public double dot(double[] that)
67 {
68 double sum = 0.0;
69 for (int i : st.keys())
70 sum += that[i] * this.get(i);
71 return sum;
72 }
73
74 public double magnitude()
75 {
76 return Math.sqrt(this.dot(this));
77 }
78
79 public class01 scale(double alpha)
80 {
81 class01 c = new class01(d);
82 for (int i : this.st.keys())
83 c.put(i, alpha * this.get(i));
84 return c;
85 }
86
87 public class01 plus(class01 that)
88 {
89 if (this.d != that.d)
90 throw new IllegalArgumentException("\n<plus> dimension disagree.\n");
91 class01 c = new class01(d); // 新建一个向量存放结果
92 for (int i : this.st.keys())
93 c.put(i, this.get(i));
94 for (int i : that.st.keys())
95 c.put(i, that.get(i) + c.get(i));
96 return c;
97 }
98
99 public String toString() // toString 接口
100 {
101 StringBuilder s = new StringBuilder();
102 for (int i : st.keys())
103 s.append("(" + i + ", " + st.get(i) + ") ");
104 return s.toString();
105 }
106
107 public static void main(String[] args)
108 {
109 class01 a = new class01(10);
110 class01 b = new class01(10);
111 a.put(3, 0.50);
112 a.put(9, 0.75);
113 a.put(6, 0.11);
114 a.put(6, 0.00);
115 b.put(3, 0.60);
116 b.put(4, 0.90);
117 StdOut.println("a = " + a);
118 StdOut.println("b = " + b);
119 StdOut.println("a dot b = " + a.dot(b));
120 StdOut.println("a + b = " + a.plus(b));
121 }
122 }
原文地址：https://www.cnblogs.com/cuancuancuanhao/p/9795441.html
时间： 2024-10-30 16:51:52