题解 | #加起来和为目标值的组合 背包#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param target int整型 
     * @param nums int整型一维数组 
     * @return int整型ArrayList<ArrayList<>>
     */
    public ArrayList<ArrayList<Integer>> combinationCount (int target, int[] nums) {
        ArrayList<ArrayList<Integer>> ans = new ArrayList<>();
        if (target == 0){
            return new ArrayList<>(ans);
        }
        process(nums, target, 0, ans, new LinkedList<>());
        return new ArrayList<>(ans);
    }

    public static void process(int[] candidates, int target, int start,
              ArrayList<ArrayList<Integer>> ans, LinkedList<Integer> list){
        if (target == 0){
//            Collections.sort(list);
            ans.add(new ArrayList<>(list));
            return;
        }

        for (int i = start; i < candidates.length; i++) {
            if (target >= candidates[i]){
                target -= candidates[i];
                list.add(candidates[i]);
                process(candidates, target, i, ans, list);
                target += candidates[i];
                list.removeLast();
            }
        }
    }
}