QuickSort_127.java

Intermediate/Quicksort_127.java

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+class QuickSort 
+{ 
+    /* This function considers last element as pivot, 
+       places the pivot element at its correct 
+       position in sorted array, and places all 
+       smaller (smaller than pivot) to left of 
+       pivot and all greater elements to right 
+       of pivot */
+    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 the 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() 
+      arr[] --> Array to be sorted, 
+      low  --> Starting index, 
+      high  --> Ending index */
+    void sort(int arr[], int low, int high) 
+    { 
+        if (low < high) 
+        { 
+            /* pi is partitioning index, arr[pi] is  
+              now at right place */
+            int pi = partition(arr, low, high); 
+
+            // Recursively sort elements before 
+            // partition and after partition 
+            sort(arr, low, pi-1); 
+            sort(arr, pi+1, high); 
+        } 
+    } 
+
+    /* 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 program 
+    public static void main(String args[]) 
+    { 
+        int arr[] = {10, 7, 8, 9, 1, 5}; 
+        int n = arr.length; 
+
+        QuickSort ob = new QuickSort(); 
+        ob.sort(arr, 0, n-1); 
+
+        System.out.println("sorted array"); 
+        printArray(arr); 
+    } 
+}