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Merging two sorted arrays

January 29, 2021

merge two sorted array

Merging two sorted arrays In Java.

Problem Statement :

Given two sorted arrays, the task is to merge them in a sorted manner.

Example :

Input:

arr1[ ]  = { 5, 8, 9}

arr2[] = {4, 7, 8}
Output:

arr3[] = {4, 5, 7, 8, 8, 9} 

Algorithm:

  • Create an array arr3[] of size n1 + n2.
  • Copy all n1 elements of arr1[] to arr3[]
  • Traverse arr2[] and one by one insert elements of arr3[] to arr1[]. This step takes O(n1 * n2) time.

Java code :

// Java program to merge two sorted arrays 
import java.util.*; 
import java.lang.*; 
import java.io.*; 

class prepinsta 
{ 
    
    public static void mergeArrays(int[] arr1, int[] arr2, int n1, 
                                int n2, int[] arr3) 
    { 
        int i = 0, j = 0, k = 0; 
    
        // Traverse both array 
        while (i<n1 && j <n2) 
        { 
            
            if (arr1[i] < arr2[j]) 
                arr3[k++] = arr1[i++]; 
            else
                arr3[k++] = arr2[j++]; 
        } 
    
        // Store remaining elements of first array 
        while (i < n1) 
            arr3[k++] = arr1[i++]; 
    
        // Store remaining elements of second array 
        while (j < n2) 
            arr3[k++] = arr2[j++]; 
    } 
    
    public static void main (String[] args) 
    { 
        int[] arr1 = { 5, 8, 9}; 
        int n1 = arr1.length; 
    
        int[] arr2 = {4, 7, 8};
        int n2 = arr2.length; 
    
        int[] arr3 = new int[n1+n2]; 
        
        mergeArrays(arr1, arr2, n1, n2, arr3); 
    
        System.out.println(“Array after merging”); 
        for (int i=0; i < n1+n2; i++) 
            System.out.print(arr3[i] + ” “); 
    } 
} 



Output:

Array after merging
1 2 3 4 5 6 7 8