Leetcode-Combinations

 1 public class Solution {
 2     public List<List<Integer>> combine(int n, int k) {
 3         List<List<Integer>> resSet = new ArrayList<List<Integer>>();
 4         if (n==0 || k==0) return resSet;
 5         List<Integer> curList = new ArrayList<Integer>();
 6         combineRecur(resSet,curList,1,k,n,k);
 7         return resSet;     
 8     }
 9    
10     public void combineRecur(List<List<Integer>> resSet, List<Integer> curList, int curIndex, int numLeft, int n, int k){
11         if (numLeft==1){
12             for (int i=curIndex;i<=n;i++){
13                 curList.add(i);
14                 List<Integer> temp = new ArrayList<Integer>();
15                 temp.addAll(curList);
16                 resSet.add(temp);
17                 curList.remove(curList.size()-1);
18             }
19             return;
20         }
21        
22 
23         for (int i=curIndex;i<=n-numLeft+1;i++){
24             curList.add(i);
25             combineRecur(resSet,curList,i+1,numLeft-1,n,k);
26             curList.remove(curList.size()-1);
27         }
28     }
29         
30 }