quicksort in c
// A full c++ quicksort algorithm no bs
// quicksort in code
#include <iostream>
using namespace std;
void QuickSort(int arr[], int start, int end);
int Partition(int arr[], int start, int end);
void SwapArrMem(int arr[], int a, int b);
int main()
{
int arr[4]; //change the size of the array to your desired array size
cout << "enter " << sizeof(arr) / sizeof(arr[0]) << " numbers. press enter after input" << endl;
for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
{
cin >> arr[i];
}
cout << endl << "The sorted numbers are:" << endl << endl;
QuickSort(arr, 0, sizeof(arr) / sizeof(arr[0]) - 1);
for (int i = 0; i < sizeof(arr) / sizeof(arr[0]); i++)
{
cout << arr[i] << endl;
}
}
void QuickSort(int arr[], int start, int end)
{
if (start >= end) return;
int index = Partition(arr, start, end);
QuickSort(arr, start, index - 1);
QuickSort(arr, index + 1, end);
}
int Partition(int arr[], int start, int end)
{
int pivotindex = start;
int pivotvalue = arr[end];
for (int i = start; i < end; i++)
{
if (arr[i] < pivotvalue)
{
SwapArrMem(arr, i, pivotindex);
pivotindex++;
}
}
SwapArrMem(arr, pivotindex, end);
return pivotindex;
}
void SwapArrMem(int arr[], int a, int b)
{
int temp = arr[a];
arr[a] = arr[b];
arr[b] = temp;
} 
#include<stdio.h>
void quicksort(int number[25],int first,int last){
int i, j, pivot, temp;
if(first<last){
pivot=first;
i=first;
j=last;
while(i<j){
while(number[i]<=number[pivot]&&i<last)
i++;
while(number[j]>number[pivot])
j--;
if(i<j){
temp=number[i];
number[i]=number[j];
number[j]=temp;
}
}
temp=number[pivot];
number[pivot]=number[j];
number[j]=temp;
quicksort(number,first,j-1);
quicksort(number,j+1,last);
}
}
int main(){
int i, count, number[25];
printf("How many elements are u going to enter?: ");
scanf("%d",&count);
printf("Enter %d elements: ", count);
for(i=0;i<count;i++)
scanf("%d",&number[i]);
quicksort(number,0,count-1);
printf("Order of Sorted elements: ");
for(i=0;i<count;i++)
printf(" %d",number[i]);
return 0;
}
/* C++ implementation of QuickSort */
#include <bits/stdc++.h>
using namespace std;
// A utility function to swap two elements
void swap(int* a, int* b)
{
int t = *a;
*a = *b;
*b = t;
}
/* This function takes 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]; // pivot
int i = (low - 1); // Index of smaller element
for (int j = low; j <= high - 1; j++)
{
// If current element is smaller than the pivot
if (arr[j] < pivot)
{
i++; // increment index of smaller element
swap(&arr[i], &arr[j]);
}
}
swap(&arr[i + 1], &arr[high]);
return (i + 1);
}
/* The main function that implements QuickSort
arr[] --> Array to be sorted,
low --> Starting index,
high --> Ending index */
void quickSort(int arr[], int low, int high)
{
if (low < high)
{
/* pi is partitioning index, arr[p] is now
at right place */
int pi = partition(arr, low, high);
// Separately sort elements before
// partition and after partition
quickSort(arr, low, pi - 1);
quickSort(arr, pi + 1, high);
}
}
/* Function to print an array */
void printArray(int arr[], int size)
{
int i;
for (i = 0; i < size; i++)
cout << arr[i] << " ";
cout << endl;
}
// Driver Code
int main()
{
int arr[] = {10, 7, 8, 9, 1, 5};
int n = sizeof(arr) / sizeof(arr[0]);
quickSort(arr, 0, n - 1);
cout << "Sorted array: \n";
printArray(arr, n);
return 0;
}
// This code is contributed by rathbhupendra
