15. 3Sum

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
      
        Arrays.sort(nums);
        int a = 0;
        ArrayList<List<Integer>> result = new ArrayList<>();
        while (a <= nums.length - 3) {
            int l = a + 1;
            int r = nums.length - 1;
            while (l < r) {
                int total = nums[a] + nums[l] + nums[r];
                if (total < 0) {
                    l++;
                    
                }
                else if (total > 0) {
                    r--;
                    
                }
                else {
                    result.add(new ArrayList<>(Arrays.asList(nums[a], nums[l], nums[r])));
                    System.out.println(a + " " + l + " " + r);
                    l++;
                    r--;
                    while (l < nums.length && nums[l] == nums[l-1]) {
                        l++;
                    }
                    while (r > a && nums[r] == nums[r+1]) {
                        r--;
                    }
                }
            }
            a++;
            while (a <= nums.length - 2 && nums[a] == nums[a-1]) {
                a++;
            }
        
        }
        return result;

    }

    
}