題目：與3數和最接近的和
Given an array S of n integers, find three integers in S such that the sum is closest to a given number, target. Return the sum of the three integers. You may assume that each input would have exactly one solution.

For example, given array S = {-1 2 1 -4}, and target = 1.

The sum that is closest to the target is 2. (-1 + 2 + 1 = 2).
 

原題連結地址：https://leetcode.com/problems/3sum-closest/
分析：題意要求從給定陣列找出和與目標數target最接近的triplet的和，該題與3Sum問題相關，可以參考一下。具體解題思想與3Sum相似。直接貼原始碼：

java程式碼（accepted)

public class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> list = new ArrayList<List<Integer>>();
        HashSet<List<Integer>> elementSet = new
 
 HashSet<List<Integer>>();
        int sum = 0;
        Arrays.sort(nums);
        for (int i = 0; i < nums.length - 2; i++) {

            int left = i + 1;
            int right = nums.length - 1;
            while (left < right) {
                sum = nums[i] + nums[left] + nums[right
 
];
                if(sum == 0){
                    List<Integer> element = new ArrayList<Integer>();
                    element.add(nums[i]);
                    element.add(nums[left]);
                    element.add(nums[right]);
                    if(!elementSet.contains(element)){
                        list.add(element);
                        elementSet.add(element);
                    }
                    left ++;
                    right --;
                }else if(sum < 0){
                    left ++;
                }else{
                    right --;
                }
            }
        }
        return list;
    }
}