[刷题]3 Sum

最新推荐文章于 2025-03-16 21:27:52 发布

原创最新推荐文章于 2025-03-16 21:27:52 发布 · 322 阅读

0 ·

CC 4.0 BY-SA版权

high frequency 专栏收录该内容

24 篇文章

订阅专栏

本文介绍了一个使用深度优先搜索(DFS)策略解决3Sum问题的Java实现方案。该方案通过递归的方式寻找数组中所有唯一三元组，使得这三个数相加等于零，并确保结果中不含重复的三元组。

[LintCode]3 Sum

public class Solution {
    /**
     * @param numbers : Give an array numbers of n integer
     * @return : Find all unique triplets in the array which gives the sum of zero.
     */
    public ArrayList<ArrayList<Integer>> threeSum(int[] numbers) {
        // 2015-10-14 DFS 
        ArrayList<ArrayList<Integer>> rst = new ArrayList<>();
        if (numbers == null || numbers.length == 0) {
            return rst;
        }
        Arrays.sort(numbers);
        ArrayList<Integer> list = new ArrayList<>();
        helper(numbers, rst, list, 0);
        return rst;
    }
    
    private void helper(int[] numbers, ArrayList<ArrayList<Integer>> rst, 
            ArrayList<Integer> list, int pos) {
        if (list.size() == 3) {
            if (list.get(0) + list.get(1) + list.get(2) == 0 
                    && !rst.contains(list)) {
                rst.add(new ArrayList<Integer>(list));
            }
            return;
        }
        for (int i = pos; i < numbers.length; i++) {
            list.add(numbers[i]);
            helper(numbers, rst, list, i + 1);
            list.remove(list.size() - 1);
        }
    }
}