三个数的和

别人的代码，总是那么优美。

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

class Solution {
    public static List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        int len = nums.length;
        if (nums == null || len < 3)
            return result;
        Arrays.sort(nums);
        for (int i = 0; i < len; i++) {
            if (nums[i] > 0)
                break;
            if (i > 0 && nums[i] == nums[i - 1]) // 去重
                continue;
            // 双指针
            int L = i + 1;
            int R = len - 1;
            while (L < R) {
                int sum = nums[i] + nums[L] + nums[R];
                if (sum == 0) {
                    result.add(Arrays.asList(nums[i], nums[L], nums[R]));
                    while (L < R && nums[L] == nums[L + 1])
                        L++;
                    while (L < R && nums[R] == nums[R - 1])
                        R--;
                    L++;
                    R--;
                } else if (sum < 0) {
                    L++;
                } else if (sum > 0) {
                    R--;
                }
            }
        }
        return result;
    }
}

public class ThreeSum {

    public static void main(String[] args) {
        Solution s = new Solution();
        int nums[] = {-1,0,1,2,-4};
        System.out.println(s.threeSum(nums));
    }

}