Java 找出一组给定数字的 n 个数字的所有组合
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/23131039/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
Find all combinations of n numbers of a given set of numbers
提问by a.s.p.
i want to write a app to find all possible combinations of n numbers of a given set of numbers and return a hashset of them.. for example if a give set{1,5,7,9} and size of set 2 then i will take:
我想编写一个应用程序来查找给定一组数字的 n 个数字的所有可能组合并返回它们的散列集。将采取：
[1, 5] [1, 7] [1, 9] [5, 7] [5, 9]
[1, 5] [1, 7] [1, 9] [5, 7] [5, 9]
i have the following code from this postbut i can't modified it for a given size of set every time.
我有这篇文章中的以下代码，但我不能每次都针对给定的集合大小修改它。
import java.util.ArrayList;
import java.util.Arrays;
class SumSet {
static void sum_up_recursive(ArrayList<Integer> numbers,ArrayList<Integer> partial) {
System.out.println("sum("+Arrays.toString(partial.toArray())+")=");
for(int i=0;i<numbers.size();i++)
{
ArrayList<Integer> remaining = new ArrayList<Integer>();
int n = numbers.get(i);
for (int j=i+1; j<numbers.size();j++)
remaining.add(numbers.get(j));
ArrayList<Integer> partial_rec = new ArrayList<Integer>(partial);
partial_rec.add(n);
sum_up_recursive(remaining,partial_rec);
}
}
static void sum_up(ArrayList<Integer> numbers) {
sum_up_recursive(numbers,new ArrayList<Integer>());
}
public static void main(String args[]) {
Integer[] numbers = {1,5,7,9};
sum_up(new ArrayList<Integer>(Arrays.asList(numbers)));
}
}
回答by niiraj874u
We can add one more parameter sizeOfset in SumSet.sum_up_recursive(ArrayList<Integer>, ArrayList<Integer>, int)method like below. please run it tell me Does it give the output what you want ?
我们可以在SumSet.sum_up_recursive(ArrayList<Integer>, ArrayList<Integer>, int)下面的方法中再添加一个参数 sizeOfset 。请运行它告诉我它是否给出了你想要的输出？
import java.util.ArrayList;
import java.util.Arrays;
public class SumSet {
static void sum_up_recursive(ArrayList<Integer> numbers,
ArrayList<Integer> partial , int sizeOfset) {
if(partial.size() == sizeOfset)
{
System.out.println("sum(" + Arrays.toString(partial.toArray()) + ")=");
}
for (int i = 0; i < numbers.size(); i++) {
ArrayList<Integer> remaining = new ArrayList<Integer>();
int n = numbers.get(i);
for (int j = i + 1; j < numbers.size(); j++)
remaining.add(numbers.get(j));
ArrayList<Integer> partial_rec = new ArrayList<Integer>(partial);
partial_rec.add(n);
sum_up_recursive(remaining, partial_rec, sizeOfset);
}
}
static void sum_up(ArrayList<Integer> numbers) {
sum_up_recursive(numbers, new ArrayList<Integer>(), 2);
}
public static void main(String args[]) {
Integer[] numbers = { 1, 5, 7, 9 };
sum_up(new ArrayList<Integer>(Arrays.asList(numbers)));
}
}
回答by juice
I changed recursive method from niiraj874u's answer to return a value. So now it gives list of hash sets as you wanted.
我从 niiraj874u 的答案中更改了递归方法以返回一个值。所以现在它可以根据需要提供哈希集列表。
static List<Set<Integer>> sum_up_recursive(List<Integer> numbers,
Set<Integer> partial , int sizeOfset) {
List<Set<Integer>> result = new ArrayList<Set<Integer>>();
if(partial.size() == sizeOfset)
result.add(partial);
for (int i = 0; i < numbers.size(); i++) {
ArrayList<Integer> remaining = new ArrayList<Integer>();
int n = numbers.get(i);
for (int j = i + 1; j < numbers.size(); j++)
remaining.add(numbers.get(j));
Set<Integer> partial_rec = new HashSet<Integer>(partial);
partial_rec.add(n);
result.addAll(sum_up_recursive(remaining, partial_rec, sizeOfset));
}
return result;
}
public static void main(String args[]) {
Integer[] numbers = { 1, 5, 7, 9 };
int size = 2;
List<Set<Integer>> allCombinations = sum_up_recursive(Arrays.asList(numbers), new HashSet<Integer>(), size);
for (Set<Integer> set : allCombinations) {
for (Integer num : set)
System.out.print(num + " ");
System.out.println();
}
}
回答by a.s.p.
thank you all... Also i found this solution
谢谢大家...我也找到了这个解决方案
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
public class Comb {
static HashSet combine(Integer[] arr, int k, int startId, int[] branch, int numElem,HashSet arrSet)
{
if (numElem == k)
{
//System.out.println("k: "+k+(Arrays.toString(branch)));
ArrayList<Integer> mySet = new ArrayList<Integer>();
for(int i=0;i<branch.length;i++)
{
mySet.add(branch[i]);
}
arrSet.add(mySet);
return arrSet;
}
for (int i = startId; i < arr.length; ++i)
{
branch[numElem++]=arr[i];
combine(arr, k, ++startId, branch, numElem, arrSet);
--numElem;
}
return arrSet;
}
public static void main(String args[])
{
int k = 3;
Integer[] input ={1,5,7,9}; "ABCD".toCharArray();
int[] branch = new int[k];//{0,0};//new char[k];
HashSet arrSet=new HashSet();
arrSet=combine(input, k, 0, branch, 0, arrSet);
}
}
回答by keerthikanth
package com.app.atb;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
public class Challenge {
public static void main(String[] args) {
Set<Integer> myset = new HashSet<Integer>();
myset.add(1);
myset.add(5);
myset.add(7);
myset.add(9);
List<Set<Integer>> achieved = solveChallenge(myset);
System.out.println(achieved);
}
public static List<Set<Integer>> solveChallenge(Set<Integer> myset) {
int n = myset.size();
Integer[] myInts = new Integer[n];
Iterator<Integer> iterator = myset.iterator();
int index = 0;
while (iterator.hasNext()) {
myInts[index] = iterator.next();
++index;
}
List<Set<Integer>> myList = new ArrayList<Set<Integer>>();
Set<Integer> subSet;
for (int i = 0; i < n; i++) {
for (int j = i; j < n; j++) {
if (j != i) {
subSet = new HashSet<Integer>();
subSet.add(myInts[i]);
subSet.add(myInts[j]);
myList.add(subSet);
}
}
}
return myList;
}
}
