package com.fishercoder.solutions;

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

/**
 * 15. 3Sum
 * Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0?
 * Find all unique triplets in the array which gives the sum of zero.

 Note: The solution set must not contain duplicate triplets.

 For example, given array S = [-1, 0, 1, 2, -1, -4],

 A solution set is:
 [
 [-1, 0, 1],
 [-1, -1, 2]
 ]
 */

public class _15 {

    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        if (nums == null || nums.length == 0) {
            return result;
        }
        Arrays.sort(nums);
        for (int i = 0; i < nums.length; i++) {
            if (i >= 1 && nums[i] == nums[i - 1]) {
                continue;
            }
            int left = i + 1;
            int right = nums.length - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (sum == 0) {
                    result.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    /**be sure to skip duplicates*/
                    while (left + 1 < right && nums[left] == nums[left + 1]) {
                        left++;
                    }
                    while (right - 1 > left && nums[right] == nums[right - 1]) {
                        right--;
                    }
                    left++;
                    right--;
                } else if (sum > 0) {
                    right--;
                } else {
                    left++;
                }
            }
        }
        return result;
    }
}

package com.fishercoder.solutions;

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

/**
 * 15. 3Sum
 * Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0?
 * Find all unique triplets in the array which gives the sum of zero.

 Note: The solution set must not contain duplicate triplets.

 For example, given array S = [-1, 0, 1, 2, -1, -4],

 A solution set is:
 [
 [-1, 0, 1],
 [-1, -1, 2]
 ]
 */

public class _15 {

    public List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> result = new ArrayList<>();
        if (nums == null || nums.length == 0) {
            return result;
        }

        Arrays.sort(nums);
        for (int i = 0; i < nums.length; i++) {
            if (i >= 1 && nums[i] == nums[i - 1]) {
                continue;
            }
            int left = i + 1;
            int right = nums.length - 1;
            while (left < right) {
                int sum = nums[i] + nums[left] + nums[right];
                if (sum == 0) {
                    result.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    /**be sure to skip duplicates*/
                    while (left + 1 < right && nums[left] == nums[left + 1]) {
                        left++;
                    }
                    while (right - 1 > left && nums[right] == nums[right - 1]) {
                        right--;
                    }
                    left++;
                    right--;
                } else if (sum > 0) {
                    right--;
                } else {
                    left++;
                }
            }
        }
        return result;
    }
}

refactor 15