#### Three Sum Problem

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```package com.thealgorithms.misc;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Scanner;
import java.util.Set;

public class ThreeSumProblem {

public static void main(String[] args) {
Scanner scan = new Scanner(System.in);
System.out.print("Enter the target sum ");
int ts = scan.nextInt();
System.out.print("Enter the number of elements in the array ");
int n = scan.nextInt();
int[] arr = new int[n];
for (int i = 0; i < n; i++) {
arr[i] = scan.nextInt();
}
ThreeSumProblem th = new ThreeSumProblem();
System.out.println("Brute Force Approach\n" + (th.bruteForce(arr, ts)) + "\n");
System.out.println("Two Pointer Approach\n" + (th.twoPointer(arr, ts)) + "\n");
System.out.println("Hashmap Approach\n" + (th.hashMap(arr, ts)));
scan.close();
}

public List<List<Integer>> bruteForce(int[] nums, int target) {
List<List<Integer>> arr = new ArrayList<List<Integer>>();

for (int i = 0; i < nums.length; i++) {
for (int j = i + 1; j < nums.length; j++) {
for (int k = j + 1; k < nums.length; k++) {
if (nums[i] + nums[j] + nums[k] == target) {
List<Integer> temp = new ArrayList<>();
Collections.sort(temp);
}
}
}
}
return arr;
}

public List<List<Integer>> twoPointer(int[] nums, int target) {
Arrays.sort(nums);
List<List<Integer>> arr = new ArrayList<List<Integer>>();
int start = 0;
int end = 0;
int i = 0;
while (i < nums.length - 1) {
start = i + 1;
end = nums.length - 1;
while (start < end) {
if (nums[start] + nums[end] + nums[i] == target) {
List<Integer> temp = new ArrayList<>();
start++;
end--;
} else if (nums[start] + nums[end] + nums[i] < target) {
start += 1;
} else {
end -= 1;
}
}
i++;
}
return new ArrayList<List<Integer>>(set);
}

public List<List<Integer>> hashMap(int[] nums, int target) {
Arrays.sort(nums);
Set<List<Integer>> ts = new HashSet<>();
HashMap<Integer, Integer> hm = new HashMap<>();

for (int i = 0; i < nums.length; i++) {
hm.put(nums[i], i);
}

for (int i = 0; i < nums.length; i++) {
for (int j = i + 1; j < nums.length; j++) {
int t = target - nums[i] - nums[j];
if (hm.containsKey(t) && hm.get(t) > j) {
List<Integer> temp = new ArrayList<>();