Combinations

Given two integers n and k, return all possible combinations of k numbers out of 1 ... n.

For example,
If n = 4 and k = 2, a solution is:

[
  [2,4],
  [3,4],
  [2,3],
  [1,2],
  [1,3],
  [1,4],
]
这道题完全是凭着感觉A出来的

public class Solution {
    private List<List<Integer>> result = new ArrayList<List<Integer>>();
    
    public List<List<Integer>> combine(int n, int k) {
        List<Integer> cur = new ArrayList<Integer>();
        
        getResult(cur, 1, 0, k, n);
       
        return result;
    }
    public void getResult(List<Integer> cur, int start, int dep, int depMax, int end){
        if(dep == depMax){
            List<Integer> temp = new ArrayList<Integer>(cur);
            result.add(temp);
        }else{
            for(int i = start; i <= end; i++){
                cur.add(i);
                getResult(cur, i + 1, dep + 1, depMax, end);
                cur.remove(cur.size() - 1);
            }
        }
    }
}