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quicksort.cpp
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quicksort.cpp
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#include <iostream>
#include <stdlib.h>
#include <ctime>
using namespace std;
int partition(int a[],int left,int right)
{
int pivot = a[left]; //taking first element as pivot
int i=left; int j=right+1;
do{
do{
i=i+1;
}while(a[i] < pivot);
do{
j=j-1;
}while(a[j] > pivot);
swap(a[i],a[j]);
}while(i<j);
swap(a[i],a[j]);
swap(a[left],a[j]);
return j;
}
void quicksort(int a[],int left,int right)
{
if(left < right)
{
int s = partition(a,left,right); // s is split position
quicksort(a,left,s-1);
quicksort(a,s+1,right);
}
}
void swap(int &x, int &y)
{
int temp;
temp = x;
x = y;
y = temp;
}
void getElements(int a[], int size)
{
for(int i=0; i<size; i++)
{
a[i] = rand()%100; // Random numbers 0-99
}
}
void display(int a[], int size)
{
for (int i=0; i<size; i++)
{
cout<<a[i]<<" ";
}
cout<<endl;
}
int main()
{
int a[500000];
int left,right;
int size;
clock_t start,end;
double totaltime;
cout<<"Enter array size: ";
cin>>size;
getElements(a,size);
//cout<<"Unsorted array: "<<endl;
//display(a,size);
start = clock();
quicksort(a,0,size-1);
end = clock();
//cout<<"Sorted array: "<<endl;
//display(a,size);
totaltime = (double)(end-start)/(CLOCKS_PER_SEC);
cout<<endl;
cout<<"The time taken is " <<totaltime<< " seconds. "<< endl;
return 0;
}