Create mergeSort.java

Author: ritik-gupta

sorting-algorithms/mergeSort.java

@@ -0,0 +1,85 @@
+import java.util.Scanner;
+
+class MergeSort { 
+ void merge(int arr[], int l, int m, int r) 
+ { 
+ int n1 = m - l + 1; 
+ int n2 = r - m;
+ int L[] = new int[n1]; 
+ int R[] = new int[n2]; 
+ 
+ for (int i = 0; i < n1; ++i) 
+ L[i] = arr[l + i]; 
+ for (int j = 0; j < n2; ++j) 
+ R[j] = arr[m + 1 + j]; 
+ 
+ int i = 0, j = 0; 
+ 
+ int k = l; 
+ 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++; 
+ } 
+ } 
+ 
+ void sort(int arr[], int l, int r) 
+ { 
+ if (l < r) { 
+ int m = (l + r) / 2; 
+ 
+ sort(arr, l, m); 
+ sort(arr, m + 1, r); 
+ 
+ merge(arr, l, m, r); 
+ } 
+ } 
+ 
+ static void printArray(int arr[]) 
+ { 
+ int n = arr.length; 
+ for (int i = 0; i < n; ++i) 
+ System.out.print(arr[i] + " "); 
+ System.out.println(); 
+ } 
+ 
+ public static void main(String args[]) 
+ { 
+ int n;
+ Scanner s = new Scanner(System.in);
+ System.out.print("Enter no. of elements you want in array:");
+ n = s.nextInt();
+ int arr[] = new int[n];
+ System.out.println("Enter all the elements:");
+ for(int i = 0; i < n; i++)
+ {
+ arr[i] = s.nextInt();
+ }
+ System.out.println("Given Array"); 
+ printArray(arr); 
+ 
+ MergeSort ob = new MergeSort(); 
+ ob.sort(arr, 0, arr.length - 1); 
+ 
+ System.out.println("\nSorted array"); 
+ printArray(arr); 
+ } 
+}