题解 | #牛牛的三元组问题#

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 nums int整型一维数组
     * @return int整型二维数组
     */
        public int[][] findTriplets (int[] candidates) {
        int n = candidates.length;
        List<List<Integer>> ans = new ArrayList<>();
        Arrays.sort(candidates);
        dfs(candidates, n, 0, 0, new ArrayList<>(), ans);
        int[][] anss = new int[ans.size()][3];
        for (int i = 0; i < ans.size(); i++) {
            List<Integer> integers = ans.get(i);
            anss[i][0] = integers.get(0);
            anss[i][1] = integers.get(1);
            anss[i][2] = integers.get(2);
        }
        return anss;
    }
    public void dfs(int[] candidate, int n, int idx, int target, List<Integer> list, List<List<Integer>> ans) {
        if (target == 0&&list.size()==3) {
            ans.add(new ArrayList<>(list));
            return ;
        }
        if (list.size()>3) return;
        for (int i = idx; i < n; i++) {
            if (i > idx && candidate[i] == candidate[i - 1]) { // 剪枝、避免重复
                // 因为前面那个同样的数已经经历过dfs，再拿同样的数dfs就会得到重复的答案
                continue;
            }
            list.add(candidate[i]);
            dfs(candidate, n, i + 1, target - candidate[i], list, ans);
            list.remove(list.size() - 1);
        }
    }
}