LeetCode48|三数之和

给定数组 nums = [-1, 0, 1, 2, -1, -4]，

满足要求的三元组集合为：
[
  [-1, 0, 1],
  [-1, -1, 2]
]

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ThreeSumTest {
    public static void main(String[] args) {
        int[] nums = {-1, 0, 1, 2, -1, -4};
        List<List<Integer>> listList = threeSum(nums);
        System.out.println("listList = " + listList);
    }

    public static List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> listList = new ArrayList<>();
        if (nums == null || nums.length == 0 || nums.length < 3) {
            return listList;
        }
        Arrays.sort(nums);
        int i = 0;
        int length = nums.length;
        while (i < length) {
            if (nums[i] > 0) {
                break;
            }
            if (i > 0 && nums[i] == nums[i - 1]) {
                i++;
                continue;
            }
            int left = i + 1;
            int right = length - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (sum == 0) {
                    listList.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    while (left < right && nums[left] == nums[left + 1]) {
                        left++;
                    }
                    while (left < right && nums[right] == nums[right - 1]) {
                        right--;
                    }
                    left++;
                    right--;
                } else if (sum < 0) {
                    left++;
                } else {
                    right--;
                }
            }
            i++;
        }
        return listList;
    }
}