[数据结构与算法]leetcode-组合总和 II

一.题目描述

给定一个数组?candidates?和一个目标数?target?，找出?candidates?中所有可以使数字和为?target?的组合。

candidates?中的每个数字在每个组合中只能使用一次。

注意：解集不能包含重复的组合。?

https://leetcode-cn.com/problems/combination-sum-ii/

二.代码

    public List<List<Integer>> combinationSum2(int[] candidates, int target) {
        int len = candidates.length;
        List<List<Integer>> res = new ArrayList<>();
        if (len == 0) {
            return res;
        }
        Arrays.sort(candidates);
        Deque<Integer> path = new ArrayDeque<>(len);
        dfs(candidates, len, 0, target, path, res);
        return res;
    }

    private void dfs(int[] candidates, int len, int begin, int target, Deque<Integer> path, List<List<Integer>> res) {
        if (target == 0) {
            res.add(new ArrayList<>(path));
            return;
        }
        for (int i = begin; i < len; i++) {
            int a = target - candidates[i];
            if (a < 0) {
                break;
            }
            if (i > begin && candidates[i] == candidates[i - 1]) {
                continue;
            }
            path.addLast(candidates[i]);
            dfs(candidates, len, i + 1, a, path, res);
            path.removeLast();
        }
    }