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Triplet Sum to Zero (medium)

Triplet Sum to Zero (medium)

Problem Statement #

Given an array of unsorted numbers, find all unique triplets in it that add up to zero.

Example 1:

Input: [-3, 0, 1, 2, -1, 1, -2]
Output: [-3, 1, 2], [-2, 0, 2], [-2, 1, 1], [-1, 0, 1]
Explanation: There are four unique triplets whose sum is equal to zero.

Example 2:

Input: [-5, 2, -1, -2, 3]
Output: [[-5, 2, 3], [-2, -1, 3]]
Explanation: There are two unique triplets whose sum is equal to zero.

Try it yourself #

Try solving this question here:

import java.util.*;
class TripletSumToZero {
  public static List<List<Integer>> searchTriplets(int[] arr) {
    List<List<Integer>> triplets = new ArrayList<>();
    // TODO: Write your code here
    return triplets;
  }
}

Solution

This problem follows the Two Pointers pattern and shares similarities with Pair with Target Sum. A couple of differences are that the input array is not sorted and instead of a pair we need to find triplets with a target sum of zero.

To follow a similar approach, first, we will sort the array and then iterate through it taking one number at a time. Let’s say during our iteration we are at number ‘X’, so we need to find ‘Y’ and ‘Z’ such that X+Y+Z==0X + Y + Z == 0 ...