39. Combination Sum

Link

Solution

DFS + backTrace

 public List<List<Integer>> combinationSum(int[] candidates, int target) {
        List<List<Integer>> finalResult = new LinkedList<>();
        List<Integer> temp = new LinkedList<>();
        helper(candidates, 0, finalResult, temp, target);
        return finalResult;
    }
    
    public void helper(int[] candidates, int index, List<List<Integer>> finalResult, List<Integer> temp, int target){
        if(target == 0){
            finalResult.add(new LinkedList(temp));
            return;
        }
        if(target < 0) return;
        
        for(int i = index; i < candidates.length; i++){
            if(target >= candidates[i]){
                target -= candidates[i];
                temp.add(candidates[i]);
                helper(candidates, i, finalResult, temp, target);
                target += candidates[i];
                temp.remove(temp.size()-1);
            }
        }
    }