110 lines
3.6 KiB
Java
110 lines
3.6 KiB
Java
import java.util.*;
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public class ThreeSumProblem {
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public static void main(String args[])
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{
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Scanner scan = new Scanner(System.in);
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System.out.print("Enter the target sum ");
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int ts= scan.nextInt();
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System.out.print("Enter the number of elements in the array ");
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int n = scan.nextInt();
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System.out.println("Enter all your array elements:");
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int arr[]= new int[n];
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for(int i=0;i<n;i++)
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{
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arr[i]=scan.nextInt();
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}
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ThreeSumProblem th = new ThreeSumProblem();
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System.out.println("Brute Force Approach\n"+(th.BruteForce(arr,ts))+"\n");
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System.out.println("Two Pointer Approach\n"+(th.TwoPointer(arr,ts))+"\n");
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System.out.println("Hashmap Approach\n"+(th.Hashmap(arr,ts)));
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}
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public List<List<Integer>> BruteForce(int[] nums,int target) {
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List<List<Integer>> arr = new ArrayList<List<Integer>>();
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for(int i=0;i<nums.length;i++)
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{
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for(int j=i+1;j<nums.length;j++)
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{
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for(int k=j+1;k<nums.length;k++)
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{
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if(nums[i]+nums[j]+nums[k]==target)
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{ List<Integer> temp = new ArrayList<>();
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temp.add(nums[i]);
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temp.add(nums[j]);
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temp.add(nums[k]);
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Collections.sort(temp);
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arr.add(temp);
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}
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}
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}
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}
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arr = new ArrayList<List<Integer>>(new LinkedHashSet<List<Integer>>(arr));
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return arr;
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}
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public List<List<Integer>> TwoPointer(int[] nums, int target) {
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Arrays.sort(nums);
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List<List<Integer>> arr = new ArrayList<List<Integer>>();
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int start=0;
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int end=0;
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int i = 0;
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while(i<nums.length-1)
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{
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start=i+1;
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end=nums.length-1;
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while (start<end)
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{
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if (nums[start]+nums[end]+nums[i]==target)
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{
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List<Integer> temp = new ArrayList<>();
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temp.add(nums[i]);
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temp.add(nums[start]);
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temp.add(nums[end]);
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arr.add(temp);
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start++;
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end--;
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}
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else if (nums[start]+nums[end]+nums[i]<target)
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start+=1;
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else
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end-=1;
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}
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i++;
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}
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Set<List<Integer>> set = new LinkedHashSet<List<Integer>>(arr);
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return new ArrayList<List<Integer>>(set);
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}
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public List<List<Integer>> Hashmap(int[] nums, int target) {
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Arrays.sort(nums);
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Set<List<Integer>> ts = new HashSet();
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HashMap<Integer,Integer> hm = new HashMap<>();
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for(int i=0;i<nums.length;i++)
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{
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hm.put(nums[i],i);
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}
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for(int i=0;i<nums.length;i++)
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{
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for(int j=i+1;j<nums.length;j++)
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{
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int t= target - nums[i] - nums[j];
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if(hm.containsKey(t) && hm.get(t)>j)
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{
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List<Integer> temp = new ArrayList<>();
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temp.add(nums[i]);
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temp.add(nums[j]);
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temp.add(t);
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ts.add(temp);
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}
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}
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}
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return new ArrayList(ts);
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}
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}
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