40. 组合总和 II

class Solution {
    List<List<Integer>> ans = new ArrayList<>();
    List<Integer> path = new ArrayList<>();
    boolean[] visited;
    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        visited = new boolean[candidates.length];
        Arrays.sort(candidates);
        dfs(candidates, target, 0);
        return ans;
    }

    private void dfs(int[] candidates, int target, int start) {
        if (target == 0) {
            ans.add(new ArrayList<>(path));
            return;
        }
        if(target<0) return;
        for (int i = start; i < candidates.length; i++) {
            //这个判断很重要，用来去重。
            //只有第一次加入的重复元素才算
            if(i>start&&candidates[i]==candidates[i-1]) continue;
            path.add(candidates[i]);
            dfs(candidates, target - candidates[i], i + 1);
            path.remove(path.size() - 1);
        }
    }
}