added bubble,selection,merge and quick sort

Sorting algorithms/BubbleSort.java

@@ -0,0 +1,30 @@
+class BubbleSort 
+{ 
+    void bubbleSort(int arr[]) 
+    { 
+        int n = arr.length; 
+        for (int i = 0; i < n-1; i++) 
+            for (int j = 0; j < n-i-1; j++) 
+                if (arr[j] > arr[j+1]) 
+                { 
+                    // swapping temp and arr[i] 
+                    int temp = arr[j]; 
+                    arr[j] = arr[j+1]; 
+                    arr[j+1] = temp; 
+                } 
+    } 
+
+    public static void main(String args[]) 
+    { 
+        BubbleSort ob = new BubbleSort(); 
+        int arr[] = {64, 34, 25, 12, 22, 11, 90}; 
+        ob.bubbleSort(arr); 
+
+        //displaying the array
+        System.out.println("The sorted array:"); 
+		int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i] + " "); 
+        System.out.println();   
+    } 
+} 

Sorting algorithms/MergeSort.java

@@ -0,0 +1,95 @@
+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++; 
+        } 
+    } 
+
+    // function that sorts arr[l..r]  
+    void sort(int arr[], int l, int r) 
+    { 
+        if (l < r) 
+        { 
+            // Finding middle point 
+            int m = (l+r)/2; 
+
+            // Sorting first half
+            sort(arr, l, m); 
+            //Sorting second half
+            sort(arr , m+1, r); 
+
+            // Merge the sorted halves 
+            merge(arr, l, m, r); 
+        } 
+    } 
+
+
+    public static void main(String args[]) 
+    { 
+        int arr[] = {5, 7, 2, 10, 17, 4, 3}; 
+
+
+        MergeSort ob = new MergeSort(); 
+        ob.sort(arr, 0, arr.length-1); 
+
+        System.out.println("\nSorted array"); 
+        int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i] + " "); 
+        System.out.println();   
+    } 
+} 

Sorting algorithms/QuickSort.java

@@ -0,0 +1,61 @@
+class QuickSort 
+{ 
+    /* Assumes a pivot element and places it correctly,
+    consequently places all elements smaller than pivot to it's left
+    and bigger elements to it's right */
+    int partition(int arr[], int low, int high) 
+    { 
+        int pivot = arr[high];  
+        int i = (low-1); // index of smaller element 
+        for (int j=low; j<high; j++) 
+        { 
+            // If current element is smaller than or 
+            // equal to pivot 
+            if (arr[j] <= pivot) 
+            { 
+                i++; 
+
+                // swap arr[i] and arr[j] 
+                int temp = arr[i]; 
+                arr[i] = arr[j]; 
+                arr[j] = temp; 
+            } 
+        } 
+
+        // swap arr[i+1] and arr[high] (or pivot) 
+        int temp = arr[i+1]; 
+        arr[i+1] = arr[high]; 
+        arr[high] = temp; 
+
+        return i+1; 
+    } 
+
+
+    // The main function that implements QuickSort() 
+
+    void sort(int arr[], int low, int high) 
+    { 
+        if (low < high) 
+        { 
+            // pi is partitioning index
+            int pi = partition(arr, low, high); 
+
+            // Recursively sorting elements before 
+            sort(arr, low, pi-1); 
+            sort(arr, pi+1, high); 
+        } 
+    } 
+
+    public static void main(String args[]) 
+    { 
+        int arr[] = {5, 7, 2, 10, 17, 4, 3}; 
+        int n = arr.length; 
+
+        QuickSort ob = new QuickSort(); 
+        ob.sort(arr, 0, n-1); 
+
+        System.out.println("sorted array"); 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i]+" "); 
+        System.out.println();     } 
+} 

Sorting algorithms/SelectionSort.java

@@ -0,0 +1,37 @@
+class SelectionSort 
+{ 
+    void sort(int arr[]) 
+    { 
+        int n = arr.length; 
+
+        // moving boundary of unsorted subarray 
+        for (int i = 0; i < n-1; i++) 
+        { 
+            // Finding the minimum element
+            int min_idx = i; 
+            for (int j = i+1; j < n; j++) 
+                if (arr[j] < arr[min_idx]) 
+                    min_idx = j; 
+
+            // Swapping minimum element with the first element 
+            int temp = arr[min_idx]; 
+            arr[min_idx] = arr[i]; 
+            arr[i] = temp; 
+        } 
+    } 
+
+       public static void main(String args[]) 
+    { 
+        SelectionSort ob = new SelectionSort(); 
+        int arr[] = {5, 7, 2, 10, 17, 4, 3}; 
+        ob.sort(arr); 
+        System.out.println("The sorted array"); 
+
+        //displaying the array
+        int n = arr.length; 
+        for (int i=0; i<n; ++i) 
+            System.out.print(arr[i]+" "); 
+        System.out.println(); 
+
+    } 
+}