今天工作中遇到一个问题需要一个组合数算法。google了一会，没有找到合适的，于是就自己写了一个。主要是用了一个递归算法。发出来分享一下，有用的着的就拿去，觉得写得不好的就拍点砖，提点建议。
import java.util.*; public class Combination { public static void main(String[] args) { Vector testData = new Vector(Arrays.asList(1, 2, 3, 4, 5, 6)); Vector results = getAllCombinations(testData); for(int i=0; i<results.size(); i++) System.out.println(results.elementAt(i)); } public static Vector getAllCombinations(Vector data) { Vector allCombinations = new Vector(); for(int i=1; i<=data.size(); i++) { Vector initialCombination = new Vector(); allCombinations.addAll(getAllCombinations(data, i)); } return allCombinations; } public static Vector getAllCombinations(Vector data, int length) { Vector allCombinations = new Vector(); Vector initialCombination = new Vector(); combination(allCombinations, data, initialCombination, length); return allCombinations; } private static void combination(Vector allCombinations, Vector data, Vector initialCombination, int length) { if(length == 1) { for(int i=0; i<data.size(); i++) { Vector newCombination = new Vector(initialCombination); newCombination.add(data.elementAt(i)); allCombinations.add(newCombination); } } if(length > 1) { for(int i=0; i<data.size(); i++) { Vector newCombination = new Vector(initialCombination); newCombination.add(data.elementAt(i)); Vector newData = new Vector(data); for(int j=0; j<=i; j++) newData.remove(data.elementAt(j)); combination(allCombinations, newData, newCombination, length - 1); } } } }
测试结果：
[1] [2] [3] [4] [5] [6] [1, 2] [1, 3] [1, 4] [1, 5] [1, 6] [2, 3] [2, 4] [2, 5] [2, 6] [3, 4] [3, 5] [3, 6] [4, 5] [4, 6] [5, 6] [1, 2, 3] [1, 2, 4] [1, 2, 5] [1, 2, 6] [1, 3, 4] [1, 3, 5] [1, 3, 6] [1, 4, 5] [1, 4, 6] [1, 5, 6] [2, 3, 4] [2, 3, 5] [2, 3, 6] [2, 4, 5] [2, 4, 6] [2, 5, 6] [3, 4, 5] [3, 4, 6] [3, 5, 6] [4, 5, 6] [1, 2, 3, 4] [1, 2, 3, 5] [1, 2, 3, 6] [1, 2, 4, 5] [1, 2, 4, 6] [1, 2, 5, 6] [1, 3, 4, 5] [1, 3, 4, 6] [1, 3, 5, 6] [1, 4, 5, 6] [2, 3, 4, 5] [2, 3, 4, 6] [2, 3, 5, 6] [2, 4, 5, 6] [3, 4, 5, 6] [1, 2, 3, 4, 5] [1, 2, 3, 4, 6] [1, 2, 3, 5, 6] [1, 2, 4, 5, 6] [1, 3, 4, 5, 6] [2, 3, 4, 5, 6] [1, 2, 3, 4, 5, 6] 相关资源：java排列组合算法