Find Pair with given Sum in the Array

Write a program that, given an array A[] of n numbers and another number x, determines whether or not there exist two elements in S whose sum is exactly x.

Solution 1st: Using sorting + binary search (nlog(n))
https://ide.geeksforgeeks.org/d4GdbW8p8J

import java.io.*;
import java.util.*;
import java.util.Arrays;

class GFG {
    public static void main (String[] args) {
        int arraySize, sumUp;
        Scanner sc = new Scanner(System.in);
        arraySize = sc.nextInt();
   
        int array[] = new int[arraySize];
        for(int i=0;i<arraySize;i++)
            array[i] = sc.nextInt();
   
        sumUp = sc.nextInt();
        Arrays.sort(array);
   
        int startIndex, endIndex;
        startIndex=0;
        endIndex=arraySize-1;
   
        while(startIndex<endIndex){
            if(array[startIndex]+array[endIndex]==sumUp)
                System.out.println(array[startIndex++] +" + "+ array[endIndex--] +" = "+sumUp);
            else if(array[startIndex]+array[endIndex]<sumUp)
                startIndex++;
            else
                endIndex--;
        }
   
        if(array[startIndex]+array[endIndex]!=sumUp)
            System.out.println("No such pair present");
    }
}

Solution 2nd: Using Hashing (O(n))
https://ide.geeksforgeeks.org/sjViggyebs

import java.io.*;
import java.util.*;
import java.util.HashSet;

class GFG {
    public static void main (String[] args) {
        int arraySize, sumUp, remainingSum;
        Scanner sc = new Scanner(System.in);
        arraySize = sc.nextInt();
   
        int array[] = new int[arraySize];
        for(int i=0;i<arraySize;i++)
            array[i] = sc.nextInt();
   
        sumUp = sc.nextInt();
        HashSet<Integer> hash = new HashSet<Integer>();
        boolean flag=false;
   
        for(int i=0; i<arraySize; i++){
            remainingSum = sumUp - array[i];
            if(hash.contains(remainingSum)){
                System.out.println(array[i]+" + "+remainingSum+" = "+sumUp);
                flag=true;
            }
            hash.add(array[i]);
        }
   
        if(flag!=true)
            System.out.println("No such pair present");
    }
}

Also, see:

Comments

  1. tachjava24 September 2019 at 13:48

    Best explanation.
    Thanks,
    https://www.flowerbrackets.com/hashset-in-java/

    ReplyDelete

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