CombinationSum39.java

public class Solution {
    
    private ArrayList<List<Integer>> res = new ArrayList<List<Integer>>();
    private ArrayList<Integer> sumr = new ArrayList<Integer>();
    
    public List<List<Integer>> combinationSum(int[] candidates, int target) {
    
        helper(candidates, target, sumr,0);
        
        return res;
        
    }
    
    public void helper(int[] list, int target, ArrayList<Integer> sumr, int sum){
        
        if(sum==target){
            ArrayList<Integer> a = new ArrayList<Integer>(sumr);
            res.add(a);
            return;
        }
        if(sum>target){
            return;
        }
        for(int i=0;i<list.length;i++){
            sumr.add(list[i]);
            sum +=list[i];
            int nl[] = Arrays.copyOfRange(list, i, list.length);
            helper(nl, target, sumr, sum);
            sum-=list[i];
            sumr.remove(sumr.size()-1);
        }
        

    }
}