#### Aim:

To write a program in C to sorting the elements using Quick sort method.

__Theory:__

The quick sort is an in-place, divide-and-conquer, massively recursive sort. As a normal person would say, it’s essentially a faster in-place version of the merge sort. The quick sort algorithm is simple in theory, but very difficult to put into code.

**The recursive algorithm consists of four steps:**

- If there are one or less elements in the array to be sorted, return immediately.
- Pick an element in the array to serve as a “pivot” point. (Usually the left-most element in the array is used.)
- Split the array into two parts – one with elements larger than the pivot and the other with elements smaller than the pivot.
- Recursively repeat the algorithm for both halves of the original array.

**The quick sort is by far the fastest of the common sorting algorithms.**

#### Algorithm:

- Get N elements which are to be sorted, and store it in the array A.
- Select the element from A[0] to A[N-1] for middle. This element is the pivot.
- Partition the remaining elements into the segments left and right so that no elements in left has a key larger than that of the pivot and no elements in right has a key smaller than that of the pivot.
- Sort left using quick sort recursively.
- Sort right using quick sort recursively.
- Display the sorted array A.

#### Program:

#include <stdio.h> #define size 100 int partition(int a[], int beg, int end); void quick_sort(int a[], int beg, int end); void main() { int arr[size], i, n; printf("\n Enter the number of elements in the array: "); scanf("%d", &n); printf("\n Enter the elements of the array: "); for(i=0;i<n;i++) { scanf("%d", &arr[i]); } quick_sort(arr, 0, n-1); printf("\n The sorted array is: \n"); for(i=0;i<n;i++) printf(" %d\t", arr[i]); } int partition(int a[], int beg, int end) { int left, right, temp, loc, flag; loc = left = beg; right = end; flag = 0; while(flag != 1) { while((a[loc] <= a[right]) && (loc!=right)) right--; if(loc==right) flag =1; else if(a[loc]>a[right]) { temp = a[loc]; a[loc] = a[right]; a[right] = temp; loc = right; } if(flag!=1) { while((a[loc] >= a[left]) && (loc!=left)) left++; if(loc==left) flag =1; else if(a[loc] <a[left]) { temp = a[loc]; a[loc] = a[left]; a[left] = temp; loc = left; } } } return loc; } void quick_sort(int a[], int beg, int end) { int loc; if(beg<end) { loc = partition(a, beg, end); quick_sort(a, beg, loc-1); quick_sort(a, loc+1, end); } }

#### Execution:

Input: 10 8 9 6 7 5 4 2 3 1 10 Output: Enter the number of elements in the array: Enter the elements of the array: The sorted array is: 1 2 3 4 5 6 7 8 9 10

#### Result:

Thus, Implement of Quick Sort was executed successfully.