Add Two Sum Problem (#2572)

Misc/TwoSumProblem.java

@@ -0,0 +1,113 @@
+import java.util.*;
+import java.util.stream.Collectors;
+public class TwoSumProblem {
+	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();
+		System.out.println("Enter all your array elements:");
+		int arr[]= new int[n];
+		for(int i=0;i<n;i++)
+		{ 
+			arr[i]=scan.nextInt();
+		}
+		TwoSumProblem t = new TwoSumProblem();
+		System.out.println("Brute Force Approach\n"+Arrays.toString(t.BruteForce(arr,ts))+"\n");
+		System.out.println("Two Pointer Approach\n"+Arrays.toString(t.TwoPointer(arr,ts))+"\n");
+		System.out.println("Hashmap Approach\n"+Arrays.toString(t.HashMap(arr,ts)));
+		
+	}
+public int[] BruteForce(int[] nums, int target) {
+	     //Brute Force Approach 
+	        int ans[]=new int[2];
+	        for (int i=0;i<nums.length;i++)
+	        {
+	            for (int j=i+1;j<nums.length;j++)
+	            {
+	                if(nums[i]+nums[j]==target)
+	                {
+	                    ans[0]=i;
+	                    ans[1]=j;
+	                   
+	                    break;
+	                }
+	                    
+	            }
+	        }
+	        
+	        return ans;
+	 }
+
+
+public int[] TwoPointer(int[] nums, int target) {		 
+		 // HashMap Approach
+		 int ans[]=new int[2];
+		 HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>();    
+	        for(int i =0;i<nums.length;i++)
+	        {
+	            hm.put(i,nums[i]);
+	        }
+	        HashMap<Integer, Integer> temp
+	            = hm.entrySet()
+	                  .stream()
+	                  .sorted((i1, i2)
+	                              -> i1.getValue().compareTo(
+	                                  i2.getValue()))
+	                  .collect(Collectors.toMap(
+	                      Map.Entry::getKey,
+	                      Map.Entry::getValue,
+	                      (e1, e2) -> e1, LinkedHashMap::new));
+	         
+	        int start = 0;
+	        int end = nums.length - 1;
+	        while (start<end)
+	        {   int currSum=(Integer) temp.values().toArray()[start]+(Integer) temp.values().toArray()[end];
+	         
+	            if(currSum==target)
+	            {   
+	                ans[0]=(Integer) temp.keySet().toArray()[start];
+	                ans[1]=(Integer) temp.keySet().toArray()[end];
+	                break;
+	            }
+	            else if(currSum>target)
+	                end-=1;
+	            else if(currSum<target)
+	            {
+	                start+=1;
+	            }
+	            
+	        }
+		 return ans;
+	        
+}
+
+
+public int[] HashMap(int[] nums, int target) {	
+	 //Using Hashmaps
+     int ans[]=new int[2];
+     HashMap<Integer,Integer> hm=new HashMap<Integer,Integer>();    
+     for(int i=0;i<nums.length;i++)
+     {
+         hm.put(nums[i],i);
+     }
+     for(int i =0;i<nums.length;i++)
+     {
+         int t = target - nums[i];
+         if(hm.containsKey(t) && hm.get(t)!=i)
+         {
+             ans[0]=i;
+             ans[1]=hm.get(t);
+             break;
+         }
+     }
+     
+     return ans;
+ }
+
+}
+	
+
+