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Merge_sort.c
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Merge_sort.c
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/* C program for Merge Sort */
#include <stdio.h>
#include <stdlib.h>
/* Merges two subarrays of arr[].
First subarray is arr[l..m]
Second subarray is arr[m+1..r]
*/
void merge(int arr[], int l, int m, int r)
{
int i, j, k;
int n1 = m - l + 1;
int n2 = r - m;
/* create temp arrays */
int L[n1], R[n2];
/* Copy data to temp arrays L[] and R[] */
for (i = 0; i < n1; i++)
L[i] = arr[l + i];
for (j = 0; j < n2; j++)
R[j] = arr[m + 1 + j];
/* Merge the temp arrays back into arr[l..r]*/
i = 0; // Initial index of first subarray
j = 0; // Initial index of second subarray
k = l; // Initial index of merged subarray
while (i < n1 && j < n2) {
if (L[i] <= R[j]) {
arr[k] = L[i];
i++;
}
else {
arr[k] = R[j];
j++;
}
k++;
}
while (i < n1) {
arr[k] = L[i];
i++;
k++;
}
while (j < n2) {
arr[k] = R[j];
j++;
k++;
}
}
/* l ----> left index to be sorted
r ----> right index to be sorted */
void mergeSort(int arr[], int l, int r)
{
if (l < r) {
// Same as (l+r)/2, but avoids overflow for
// large l and h
int m = l + (r - l) / 2;
// Sort first and second halves
mergeSort(arr, l, m);
mergeSort(arr, m + 1, r);
merge(arr, l, m, r);
}
}
/* Function to print an array */
void printArray(int A[], int size)
{
int i;
for (i = 0; i < size; i++)
printf("%d ", A[i]);
printf("\n");
}
/* Driver code */
int main()
{
int i, n;
printf("Enter the number of elements in the array : ");
scanf("%d",&n);
int arr[n];
printf("Enter the elements in the array : ");
for(i = 0;i<n;i++){
scanf("%d",&arr[i]);
}
printf("Entered array is : ");
printArray(arr, n);
printf("\n");
mergeSort(arr, 0, n - 1);
printf("Sorted array is : ");
printArray(arr, n);
return 0;
}