Added mergesort

mergesort.c

@@ -0,0 +1,91 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+
+
+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++;
+	}
+
+	/* Copy the remaining elements of L[], if there
+	are any */
+	while (i < n1) {
+		arr[k] = L[i];
+		i++;
+		k++;
+	}
+
+	/* Copy the remaining elements of R[], if there
+	are any */
+	while (j < n2) {
+		arr[k] = R[j];
+		j++;
+		k++;
+	}
+}
+
+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);
+	}
+}
+
+
+void printArray(int A[], int size)
+{
+	int i;
+	for (i = 0; i < size; i++)
+		printf("%d ", A[i]);
+	printf("\n");
+}
+
+int main()
+{
+	int arr[] = { 12, 11, 13, 5, 6, 7 };
+	int arr_size = sizeof(arr) / sizeof(arr[0]);
+
+	printf("Given array is \n");
+	printArray(arr, arr_size);
+
+	mergeSort(arr, 0, arr_size - 1);
+
+	printf("\nSorted array is \n");
+	printArray(arr, arr_size);
+	return 0;
+}