Merge pull request tulika-99#64 from Ashraf-101/master

Added shell sort Java version

Author: tulika-99

Shell sort/explaination.txt

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+ShellSort is mainly a variation of Insertion Sort. In insertion sort, we move elements only one position ahead. When an element has to be moved far ahead, many movements are involved. The idea of shellSort is to allow exchange of far items. In shellSort, we make the array h-sorted for a large value of h. We keep reducing the value of h until it becomes 1. An array is said to be h-sorted if all sublists of every h’th element is sorted.

Shell sort/shellsort-java.txt

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+class ShellSort 
+{ 
+    /* An 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(); 
+    } 
+  
+    /* function to sort arr using shellSort */
+    int sort(int arr[]) 
+    { 
+        int n = arr.length; 
+  
+        // Start with a big gap, then reduce the gap 
+        for (int gap = n/2; gap > 0; gap /= 2) 
+        { 
+            // Do a gapped insertion sort for this gap size. 
+            // The first gap elements a[0..gap-1] are already 
+            // in gapped order keep adding one more element 
+            // until the entire array is gap sorted 
+            for (int i = gap; i < n; i += 1) 
+            { 
+                // add a[i] to the elements that have been gap 
+                // sorted save a[i] in temp and make a hole at 
+                // position i 
+                int temp = arr[i]; 
+  
+                // shift earlier gap-sorted elements up until 
+                // the correct location for a[i] is found 
+                int j; 
+                for (j = i; j >= gap && arr[j - gap] > temp; j -= gap) 
+                    arr[j] = arr[j - gap]; 
+  
+                // put temp (the original a[i]) in its correct 
+                // location 
+                arr[j] = temp; 
+            } 
+        } 
+        return 0; 
+    } 
+  
+    // Driver method 
+    public static void main(String args[]) 
+    { 
+        int arr[] = {12, 34, 54, 2, 3}; 
+        System.out.println("Array before sorting"); 
+        printArray(arr); 
+  
+        ShellSort ob = new ShellSort(); 
+        ob.sort(arr); 
+  
+        System.out.println("Array after sorting"); 
+        printArray(arr); 
+    } 
+}