Leetcode-Blind75/15.3-sum.java at main · pranav2579/Leetcode-Blind75 · GitHub

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/*
 * @lc app=leetcode id=15 lang=java
 *
 * [15] 3Sum
 */

// @lc code=start
class Solution {
    public List<List<Integer>> threeSum(int[] nums) {
        Set<List<Integer>> res = new HashSet<>();
        Set<Integer> dups = new HashSet<>();
        Map<Integer, Integer> seen = new HashMap<>();
        for (int i = 0; i < nums.length; ++i)
            if (dups.add(nums[i])) {
                for (int j = i + 1; j < nums.length; ++j) {
                    int complement = -nums[i] - nums[j];
                    if (seen.containsKey(complement) && seen.get(complement) == i) {
                        List<Integer> triplet = Arrays.asList(nums[i], nums[j], complement);
                        Collections.sort(triplet);
                        res.add(triplet);
                    }
                    seen.put(nums[j], i);
                }
            }

        return new ArrayList(res);
    }
}
// @lc code=end