[LeetCode] Combination Sum

Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T. 

解题思路：recursion

Java Code:

public List<List<Integer>> combinationSum(int[] candidates, int target) {
        Arrays.sort(candidates);
        List> res = new ArrayList>();
        List solution = new ArrayList();
        
        combination(candidates, 0, target, res, solution);
        
        return res;
    }
    
    public void combination(int[] candidates, int startIndex, int target, List> res, List solution){
        if(target == 0){
            List tmp = new ArrayList(solution);
            res.add(tmp);
            return;
        }
        
        for(int i = startIndex; i < candidates.length; i++){
            if(candidates[i] <= target){
                solution.add(candidates[i]);
                combination(candidates, i, target - candidates[i], res, solution);
                solution.remove(solution.size() - 1);
            }else break;
        }
    }