Merge pull request #7 from ankurpalmia/master

merge_sort.java

Author: darpanjbora

Sorting Algorithms/merge_sort.java

@@ -0,0 +1,103 @@
+class MergeSort 
+{ 
+    // 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) 
+    { 
+        // Find sizes of two subarrays to be merged 
+        int n1 = m - l + 1; 
+        int n2 = r - m; 
+  
+        /* Create temp arrays */
+        int L[] = new int [n1]; 
+        int R[] = new int [n2]; 
+  
+        /*Copy data to temp arrays*/
+        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]; 
+  
+  
+        /* Merge the temp arrays */
+  
+        // Initial indexes of first and second subarrays 
+        int i = 0, j = 0; 
+  
+        // Initial index of merged subarry array 
+        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++; 
+        } 
+  
+        /* Copy remaining elements of L[] if any */
+        while (i < n1) 
+        { 
+            arr[k] = L[i]; 
+            i++; 
+            k++; 
+        } 
+  
+        /* Copy remaining elements of R[] if any */
+        while (j < n2) 
+        { 
+            arr[k] = R[j]; 
+            j++; 
+            k++; 
+        } 
+    } 
+  
+    // Main function that sorts arr[l..r] using 
+    // merge() 
+    void sort(int arr[], int l, int r) 
+    { 
+        if (l < r) 
+        { 
+            // Find the middle point 
+            int m = (l+r)/2; 
+  
+            // Sort first and second halves 
+            sort(arr, l, m); 
+            sort(arr , m+1, r); 
+  
+            // Merge the sorted halves 
+            merge(arr, l, m, r); 
+        } 
+    } 
+  
+    /* A utility function to print array of size n */
+    static void printArray(int arr[]) 
+    { 
+        int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i] + " "); 
+        System.out.println(); 
+    } 
+  
+    // Driver method 
+    public static void main(String args[]) 
+    { 
+        int arr[] = {12, 11, 13, 5, 6, 7}; 
+  
+        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); 
+    } 
+}