Merge pull request #32 from atishaya11/master

Added Implementation of quick sort

Sorts/QuickSort.c

@@ -0,0 +1,100 @@
+#include <stdio.h>
+
+/*Displays the array, passed to this method*/
+
+void display(int arr[], int n){
+
+	int i;
+	for(i = 0; i < n; i++){
+		printf("%d ", arr[i]);
+	}
+
+	printf("\n");
+
+}
+
+/*Swap function to swap two values*/
+void swap(int *first, int *second){
+
+	int temp = *first;
+	*first = *second;
+	*second = temp;
+	
+}
+
+
+/*Partition method which selects a pivot
+  and places each element which is less than the pivot value to its left
+  and the elements greater than the pivot value to its right
+
+  arr[] --- array to be partitioned
+  lower --- lower index 
+  upper --- upper index
+*/
+int partition(int arr[], int lower, int upper){
+
+	int i = (lower  - 1);
+
+	int pivot = arr[upper];	// Selects last element as the pivot value
+
+	int j ;	
+	for(j = lower; j < upper ; j++){
+
+		if(arr[j] <= pivot){ // if current element is smaller than the pivot
+
+			i++; // increment the index of smaller element
+			swap(&arr[i], &arr[j]);
+		}
+	}
+
+	swap(&arr[i + 1] , &arr[upper]); // places the last element i.e, the pivot to its correct position
+   
+	return (i + 1); 
+}
+
+
+/*This is where the sorting of the array takes place
+	arr[] --- Array to be sorted
+	lower --- Starting index
+	upper --- Ending index
+*/
+void quickSort(int arr[], int lower,  int upper){
+
+	if(upper > lower){
+
+		// partitioning index is returned by the partition method , partition element is at its correct poition
+
+		int partitionIndex = partition(arr, lower, upper); 
+
+
+		// Sorting elements before and after the partition index
+		quickSort(arr, lower, partitionIndex - 1);
+		quickSort(arr, partitionIndex + 1, upper);
+	}
+}
+
+
+int main(){
+
+
+	int n;
+	printf("Enter size of array:\n");
+	scanf("%d", &n); // E.g. 8
+
+	printf("Enter the elements of the array\n");
+	int i;
+	int arr[n];
+	for(i = 0; i < n; i++){
+		scanf("%d", &arr[i] ); 
+	}
+
+	printf("Original array: "); 
+	display(arr, n);       			// Original array : 10 11 9 8 4 7 3 8
+
+	quickSort(arr, 0, n-1);
+
+	printf("Sorted array: "); 
+	display(arr, n);				// Sorted array : 3 4 7 8 8 9 10 11
+
+	return 0;
+}