Question: We have 2 sorted arrays and we want to combine them into a single sorted array.

Input: arr1[] = 1, 4, 6, 8, 13, 25 || arr2[] = 2, 7, 10, 11, 19, 50

Output: 1, 2, 4, 6, 7, 8, 10, 11, 13, 19, 50

One of the simplest ways to solve this problem would be to copy both the arrays into a new array and then apply some sorting technique on them. But this method will not utilize the fact that both the arrays are already sorted.

We need to apply a different approach. Here is the algorithm that we can implement.

- Initialize two variables that serve as an index to both the arrays.
- Let
**i**point to arr1[] and**j**point to arr2[]. - Compare arr[i] and arr[j]
- Add the smaller element to the new array and increase the counter.
- Repeat these steps until both counters
**i & j**have reached the end.

Here is an implementation of the above algorithm

#include<stdio.h> //a function to merge two arrays //array1 is of size 'l' //array2 is of size 'm' //array3 is of size n=l+m void merge(int arr1[], int arr2[], int arr3[], int l, int m, int n) { //3 counters to point at indexes of 3 arrays int i,j,k; i=j=k=0; //loop until the array 1 and array 2 are within bounds while(i<l && j<m) { //find the smaller element among the two //and increase the counter if(arr1[i] < arr2[j]) { arr3[k] = arr1[i]; //increment counter of 1st array i++; } else { arr3[k] = arr2[j]; //increment counter of second array j++; } //increase the counter of the final array k++; } //now fill the remaining elements as it is since they are //already sorted while(i<l) { arr3[k] = arr1[i]; i++; k++; } while(j<m) { arr3[k] = arr2[j]; j++; k++; } } //driver program to test the above function int main(void) { int arr1[5] = {1, 5, 9, 11, 15}; int arr2[5] = {2, 4, 13, 99, 100}; int arr3[10] = {0}; merge(arr1, arr2, arr3, 5, 5, 10); int i=0; for(i=0;i<10;i++) printf("%d ",arr3[i]); return 0; }