15. 3Sum

[Luchanaaaaa]

java

class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Arrays.sort(nums);
        List<List<Integer>> ans = new ArrayList<>();
        for(int i = 0; i < nums.length; i++){
            if(i > 0 && nums[i] == nums[i-1]) continue;
            int left = i + 1, right = nums.length - 1;
            int num1 = nums[i];

            while(left < right){
                int num2 = nums[left], num3 = nums[right];
                int sum = num1 + num2 + num3; 
                if(left -1 > i && nums[left -1] == nums[left]){
                    left++;
                    continue;
                }
                if(sum == 0) {
                    ans.add(Arrays.asList(num1, num2, num3));
                    left++;
                }
                else if(sum > 0) right--;
                else if(sum < 0) left++;
            }

        }
        return ans;

    }
}