? 书中第三章部分程序，加上自己补充的代码，包括散列表、线性探查表
● 散列表
1 package package01;
2
3 import edu.princeton.cs.algs4.Queue;
4 import edu.princeton.cs.algs4.SequentialSearchST;
5 import edu.princeton.cs.algs4.StdIn;
6 import edu.princeton.cs.algs4.StdOut;
7
8 public class class01<Key, Value>
9 {
10 private static final int INIT_CAPACITY = 4; // 默认构造函数参数
11 private int n; // 待插入元素数
12 private int m; // 散列表尺寸
13 private SequentialSearchST<Key, Value>[] st; // 散列表
14
15 public class01()
16 {
17 this(INIT_CAPACITY);
18 }
19
20 public class01(int capacity)
21 {
22 m = capacity;
23 st = (SequentialSearchST<Key, Value>[]) new SequentialSearchST[m];
24 for (int i = 0; i < m; i++)
25 st[i] = new SequentialSearchST<Key, Value>();
26 }
27
28 public int size()
29 {
30 return n;
31 }
32
33 public boolean isEmpty()
34 {
35 return size() == 0;
36 }
37
38 private void resize(int capacity)
39 {
40 class01<Key, Value> temp = new class01<Key, Value>(capacity);
41 for (int i = 0; i < m; i++)
42 {
43 for (Key key : st[i].keys())
44 temp.put(key, st[i].get(key));
45 }
46 m = temp.m;
47 n = temp.n;
48 st = temp.st;
49 }
50
51 public boolean contains(Key key)
52 {
53 if (key == null)
54 throw new IllegalArgumentException("\n<contains> key == null.\n");
55 return get(key) != null;
56 }
57
58 private int hash(Key key)
59 {
60 return (key.hashCode() & 0x7fffffff) % m;
61 }
62
63 public Value get(Key key)
64 {
65 if (key == null)
66 throw new IllegalArgumentException("\n<get> key == null.\n");
67 return st[hash(key)].get(key);
68 }
69
70 public void put(Key key, Value val)
71 {
72 if (key == null)
73 throw new IllegalArgumentException("\n<get> key == null.\n");
74 if (val == null)
75 {
76 delete(key);
77 return;
78 }
79 if (n >= 10 * m) // 平均链表长度不小于 10，扩容
80 resize(2 * m);
81 int i = hash(key);
82 if (!st[i].contains(key))
83 n++;
84 st[i].put(key, val);
85 }
86
87 public void delete(Key key)
88 {
89 if (key == null)
90 throw new IllegalArgumentException("\n<delete> key == null.\n");
91 if (!contains(key))
92 return;
93 int i = hash(key);
94 if (st[i].contains(key))
95 n--;
96 st[i].delete(key);
97 if (m > INIT_CAPACITY && n <= 2 * m) // 平均链表长度小于 2，缩容
98 resize(m / 2);
99 }
100
101 public Iterable<Key> keys()
102 {
103 Queue<Key> queue = new Queue<Key>();
104 for (int i = 0; i < m; i++)
105 {
106 for (Key key : st[i].keys())
107 queue.enqueue(key);
108 }
109 return queue;
110 }
111
112 public static void main(String[] args)
113 {
114 class01<String, Integer> st = new class01<String, Integer>();
115 for (int i = 0; !StdIn.isEmpty(); i++)
116 {
117 String key = StdIn.readString();
118 st.put(key, i);
119 }
120 for (String s : st.keys())
121 StdOut.println(s + " " + st.get(s));
122 }
123 }
● 线性探查表
1 package package01;
2
3 import edu.princeton.cs.algs4.Queue;
4 import edu.princeton.cs.algs4.StdIn;
5 import edu.princeton.cs.algs4.StdOut;
6
7 public class class01<Key, Value>
8 {
9 private static final int INIT_CAPACITY = 4;
10 private int n;
11 private int m;
12 private Key[] keys;
13 private Value[] vals;
14
15 public class01()
16 {
17 this(INIT_CAPACITY);
18 }
19
20 public class01(int capacity)
21 {
22 m = capacity;
23 n = 0;
24 keys = (Key[]) new Object[m];
25 vals = (Value[]) new Object[m];
26 }
27
28 public int size()
29 {
30 return n;
31 }
32
33 public boolean isEmpty()
34 {
35 return size() == 0;
36 }
37
38 private void resize(int capacity)
39 {
40 class01<Key, Value> temp = new class01<Key, Value>(capacity);
41 for (int i = 0; i < m; i++)
42 {
43 if (keys[i] != null)
44 temp.put(keys[i], vals[i]);
45 }
46 m = temp.m;
47 keys = temp.keys;
48 vals = temp.vals;
49
50 }
51
52 public boolean contains(Key key)
53 {
54 if (key == null)
55 throw new IllegalArgumentException("\n<contains> key == null.\n");
56 return get(key) != null;
57 }
58
59 private int hash(Key key)
60 {
61 return (key.hashCode() & 0x7fffffff) % m;
62 }
63
64 public Value get(Key key)
65 {
66 if (key == null)
67 throw new IllegalArgumentException("\n<get> key == null.\n");
68 for (int i = hash(key); keys[i] != null; i = (i + 1) % m) // 表荷载不会超过 1/2，所以不会绕圈
69 {
70 if (keys[i].equals(key))
71 return vals[i];
72 }
73 return null;
74 }
75
76 public void put(Key key, Value val)
77 {
78 if (key == null)
79 throw new IllegalArgumentException("\n<get> key == null.\n");
80 if (val == null)
81 {
82 delete(key);
83 return;
84 }
85 if (n >= m / 2) // 荷载超过一半了，扩容
86 resize(2 * m);
87 int i;
88 for (i = hash(key); keys[i] != null; i = (i + 1) % m)
89 {
90 if (keys[i].equals(key))
91 {
92 vals[i] = val;
93 return;
94 }
95 }
96 keys[i] = key;
97 vals[i] = val;
98 n++;
99 }
100
101 public void delete(Key key)
102 {
103 if (key == null)
104 throw new IllegalArgumentException("\n<delete> key == null.\n");
105 if (!contains(key))
106 return;
107 int i = hash(key);
108 for (; !key.equals(keys[i]); i = (i + 1) % m); // 找到目标元素
109 keys[i] = null; // 删除目标元素
110 vals[i] = null;
111 for (i = (i + 1) % m; keys[i] != null; i = (i + 1) % m) // 在下一个 null 之前，所有元素重新插入
112 {
113 Key keyToRehash = keys[i];
114 Value valToRehash = vals[i];
115 keys[i] = null;
116 vals[i] = null;
117 n--;
118 put(keyToRehash, valToRehash);
119 }
120 n--;
121 if (n > 0 && n <= m / 8) // 荷载小于 1/8， 缩容
122 resize(m / 2);
123 }
124
125 public Iterable<Key> keys()
126 {
127 Queue<Key> queue = new Queue<Key>();
128 for (int i = 0; i < m; i++)
129 {
130 if (keys[i] != null)
131 queue.enqueue(keys[i]);
132 }
133 return queue;
134 }
135 private boolean check()
136 {
137 if (m < 2 * n) // 检查容量
138 {
139 System.err.println("\n<check> m < 2 * n.\n");
140 return false;
141 }
142 for (int i = 0; i < m; i++) // 检查 hash
143 {
144 if (keys[i] == null)
145 continue;
146 if (get(keys[i]) != vals[i])
147 {
148 System.err.println("\n<check> hash error at i = ", i, ", key[i] = ", get(keys[i]), ", val[i] = ", vals[i], ".\n");
149 return false;
150 }
151 }
152 return true;
153 }
154
155 public static void main(String[] args)
156 {
157 class01<String, Integer> st = new class01<String, Integer>();
158 for (int i = 0; !StdIn.isEmpty(); i++)
159 {
160 String key = StdIn.readString();
161 st.put(key, i);
162 }
163 for (String s : st.keys())
164 StdOut.println(s + " " + st.get(s));
165 }
166 }
原文地址：https://www.cnblogs.com/cuancuancuanhao/p/9795423.html
时间： 2024-10-13 03:07:25