JAVA：发电机组,子集长度在3到最大之间
作者：互联网
一切都在标题中.. =)
我想快速创建一个powerset,只有长度在3(最小常数长度)和最大值之间的子集.这个最大值应该是大多数时间的5,但我希望它变量(从3到5,6).
原始集可能很大.我需要存储这些子集以供进一步处理.
我见过Obtaining a powerset of a set in Java,但在这里他们生成了电源组的每个子集.
我也看过efficient powerset algorithm for subsets of minimal length,对于C#,但我认为,正如Adam S所说,我将遇到低运行时间性能和内存问题.
我想将这些想法结合到一个理想的想法中.我最后的希望是快速生成每个子集(可能使用Guava中的算法)并迭代以仅采用所需的长度…但即使阅读它也很难看;)
有人有想法吗？
解决方法:
基本上,当我遍历控制集合生成的位数组时,我检查以确保位数在最小值和最大值之间.
这是代码.
import java.util.BitSet;
import java.util.Iterator;
import java.util.Set;
import java.util.TreeSet;
public class PowerSet<E> implements Iterator<Set<E>>, Iterable<Set<E>> {
private int minSize;
private int maxSize;
private E[] arr = null;
private BitSet bset = null;
@SuppressWarnings("unchecked")
public PowerSet(Set<E> set, int minSize, int maxSize) {
this.minSize = Math.min(minSize, set.size());
this.maxSize = Math.min(maxSize, set.size());
arr = (E[]) set.toArray();
bset = new BitSet(arr.length + 1);
for (int i = 0; i < minSize; i++) {
bset.set(i);
}
}
@Override
public boolean hasNext() {
return !bset.get(arr.length);
}
@Override
public Set<E> next() {
Set<E> returnSet = new TreeSet<E>();
// System.out.println(printBitSet());
for (int i = 0; i < arr.length; i++) {
if (bset.get(i)) {
returnSet.add(arr[i]);
}
}
int count;
do {
incrementBitSet();
count = countBitSet();
} while ((count < minSize) || (count > maxSize));
// System.out.println(returnSet);
return returnSet;
}
protected void incrementBitSet() {
for (int i = 0; i < bset.size(); i++) {
if (!bset.get(i)) {
bset.set(i);
break;
} else
bset.clear(i);
}
}
protected int countBitSet() {
int count = 0;
for (int i = 0; i < bset.size(); i++) {
if (bset.get(i)) {
count++;
}
}
return count;
}
protected String printBitSet() {
StringBuilder builder = new StringBuilder();
for (int i = 0; i < bset.size(); i++) {
if (bset.get(i)) {
builder.append('1');
} else {
builder.append('0');
}
}
return builder.toString();
}
@Override
public void remove() {
throw new UnsupportedOperationException("Not Supported!");
}
@Override
public Iterator<Set<E>> iterator() {
return this;
}
public static void main(String[] args) {
Set<Character> set = new TreeSet<Character>();
for (int i = 0; i < 7; i++)
set.add((char) (i + 'A'));
PowerSet<Character> pset = new PowerSet<Character>(set, 3, 5);
int count = 1;
for (Set<Character> s : pset) {
System.out.println(count++ + ": " + s);
}
}
}
以下是测试结果：
1: [A, B, C]
2: [A, B, D]
3: [A, C, D]
4: [B, C, D]
5: [A, B, C, D]
6: [A, B, E]
7: [A, C, E]
8: [B, C, E]
9: [A, B, C, E]
10: [A, D, E]
11: [B, D, E]
12: [A, B, D, E]
13: [C, D, E]
14: [A, C, D, E]
15: [B, C, D, E]
16: [A, B, C, D, E]
17: [A, B, F]
18: [A, C, F]
19: [B, C, F]
20: [A, B, C, F]
21: [A, D, F]
22: [B, D, F]
23: [A, B, D, F]
24: [C, D, F]
25: [A, C, D, F]
26: [B, C, D, F]
27: [A, B, C, D, F]
28: [A, E, F]
29: [B, E, F]
30: [A, B, E, F]
31: [C, E, F]
32: [A, C, E, F]
33: [B, C, E, F]
34: [A, B, C, E, F]
35: [D, E, F]
36: [A, D, E, F]
37: [B, D, E, F]
38: [A, B, D, E, F]
39: [C, D, E, F]
40: [A, C, D, E, F]
41: [B, C, D, E, F]
42: [A, B, G]
43: [A, C, G]
44: [B, C, G]
45: [A, B, C, G]
46: [A, D, G]
47: [B, D, G]
48: [A, B, D, G]
49: [C, D, G]
50: [A, C, D, G]
51: [B, C, D, G]
52: [A, B, C, D, G]
53: [A, E, G]
54: [B, E, G]
55: [A, B, E, G]
56: [C, E, G]
57: [A, C, E, G]
58: [B, C, E, G]
59: [A, B, C, E, G]
60: [D, E, G]
61: [A, D, E, G]
62: [B, D, E, G]
63: [A, B, D, E, G]
64: [C, D, E, G]
65: [A, C, D, E, G]
66: [B, C, D, E, G]
67: [A, F, G]
68: [B, F, G]
69: [A, B, F, G]
70: [C, F, G]
71: [A, C, F, G]
72: [B, C, F, G]
73: [A, B, C, F, G]
74: [D, F, G]
75: [A, D, F, G]
76: [B, D, F, G]
77: [A, B, D, F, G]
78: [C, D, F, G]
79: [A, C, D, F, G]
80: [B, C, D, F, G]
81: [E, F, G]
82: [A, E, F, G]
83: [B, E, F, G]
84: [A, B, E, F, G]
85: [C, E, F, G]
86: [A, C, E, F, G]
87: [B, C, E, F, G]
88: [D, E, F, G]
89: [A, D, E, F, G]
90: [B, D, E, F, G]
91: [C, D, E, F, G]
标签：java,powerset 来源： https://codeday.me/bug/20190620/1244926.html