Merge pull request #4 from ramvikrams/QSA

quickSort algorithm in c++

quickSort.cpp

@@ -0,0 +1,80 @@
+// Quick sort in C++
+
+#include <iostream>
+using namespace std;
+
+// function to swap elements
+void swap(int *a, int *b) {
+ int t = *a;
+ *a = *b;
+ *b = t;
+}
+
+// function to print the array
+void printArray(int array[], int size) {
+ int i;
+ for (i = 0; i < size; i++)
+ cout << array[i] << " ";
+ cout << endl;
+}
+
+// function to rearrange array (find the partition point)
+int partition(int array[], int low, int high) {
+
+ // select the rightmost element as pivot
+ int pivot = array[high];
+
+ // pointer for greater element
+ int i = (low - 1);
+
+ // traverse each element of the array
+ // compare them with the pivot
+ for (int j = low; j < high; j++) {
+ if (array[j] <= pivot) {
+
+ // if element smaller than pivot is found
+ // swap it with the greater element pointed by i
+ i++;
+
+ // swap element at i with element at j
+ swap(&array[i], &array[j]);
+ }
+ }
+
+ // swap pivot with the greater element at i
+ swap(&array[i + 1], &array[high]);
+
+ // return the partition point
+ return (i + 1);
+}
+
+void quickSort(int array[], int low, int high) {
+ if (low < high) {
+
+ // find the pivot element such that
+ // elements smaller than pivot are on left of pivot
+ // elements greater than pivot are on righ of pivot
+ int pi = partition(array, low, high);
+
+ // recursive call on the left of pivot
+ quickSort(array, low, pi - 1);
+
+ // recursive call on the right of pivot
+ quickSort(array, pi + 1, high);
+ }
+}
+
+// Driver code
+int main() {
+ int data[] = {8, 7, 6, 1, 0, 9, 2};
+ int n = sizeof(data) / sizeof(data[0]);
+
+ cout << "Unsorted Array: \n";
+ printArray(data, n);
+
+ // perform quicksort on data
+ quickSort(data, 0, n - 1);
+
+ cout << "Sorted array in ascending order: \n";
+ printArray(data, n);
+}