用递归写的，使用时要注意栈空间问题
/**
* 从m个里取n个的所有组合 c(m,n)
*
* @param m
* @param n
* @return
*/
public static List<List<Integer>> getCombinationList(int m, int n) {
if (n == 1) {
List<List<Integer>> resultList = new ArrayList<List<Integer>>();
for (int i = 1; i <= m; i++) {
resultList.add(new ArrayList<Integer>(Arrays.asList(i)));
}
return resultList;
}
List<List<Integer>> nMinusOneCombList = getCombinationList(m, n - 1);
List<List<Integer>> resultList = new ArrayList<List<Integer>>();
for (List<Integer> nMinusOneComb : nMinusOneCombList) {
for (int number = 1; number <= m; number++) {
List<Integer> comb = new ArrayList<Integer>();
comb.addAll(nMinusOneComb);
Integer maxOfNminusOneComb = nMinusOneComb.get(nMinusOneComb.size() - 1);
if (number <= maxOfNminusOneComb) {
continue;
}
comb.add(number);
resultList.add(comb);
}
}
return resultList;
}
public static void main(String[] args) {
List<List<Integer>> resultList = getCombinationList(4, 2);
for (List<Integer> list : resultList) {
System.out.println(list);
}
}
执行main后输出：
[1, 2]
[1, 3]
[1, 4]
[2, 3]
[2, 4]
[3, 4]