Question

c++ data structures please

Pick any inefficient sorting algorithm you want, selection, bubble, insertion, etc., and implement it as a function. Using the system clock as a timer, determine when the efficiency of the algorithm breaks down. For example, does it become slow after 1000 elements, 10000 elements, 100000 elements? Write some code to figure this out. Then use the sort() algorithm that is part of the STL <algorithm> library. How does this function compare to the function you implemented? Also, compare the speeds of your implemented sort with the built-in sort function. Have each function sort one million randomly-generated integers. What are the times for these two functions?

Answer 1

CPP CODE:

#include<iostream>
#include<algorithm>
#include<time.h>
using namespace std;
void selectionsort(int arr[],int n)
{
for(int i=0;i<n;i++)
{
for(int j=i+1;j<n;j++)
{
if(arr[i]>arr[j])
swap(arr[i],arr[j]);
}
}
}
int main()
{
srand(time(0));
//1000 elements
int arr1[1000];
for(int i=0;i<1000;i++)
arr1[i]=rand();
clock_t t;
t=clock();
selectionsort(arr1,1000);
t=clock()-t;
double time_taken1 = ((double)t)/CLOCKS_PER_SEC;
//10000 elements
int arr2[10000];
for(int i=0;i<10000;i++)
arr2[i]=rand();
t=clock();
selectionsort(arr2,10000);
t=clock()-t;
double time_taken2 = ((double)t)/CLOCKS_PER_SEC;
//1000000 elements
int arr3[100000];
int brr3[100000];
for(int i=0;i<100000;i++)
{
arr3[i]=rand();
brr3[i]=arr3[i];
}
t=clock();
selectionsort(arr3,100000);
t=clock()-t;
double time_taken3 = ((double)t)/CLOCKS_PER_SEC;
double pertime1=time_taken1/1000;
double pertime2=time_taken2/10000;
double pertime3=time_taken3/100000;
cout<<fixed<<"Time taken to selection sort 1000 random elements: "<<time_taken1<<" seconds Time in seconds per element: "<<pertime1<<endl;
cout<<fixed<<"Time taken to selection sort 10000 random elements: "<<time_taken2<<" seconds Time in seconds per element: "<<pertime2<<endl;
cout<<fixed<<"Time taken to selection sort 100000 random elements: "<<time_taken3<<" seconds Time in seconds per element: "<<pertime3<<endl;
//Now sort 100000 elements using STL's sort function
t=clock();
sort(brr3,brr3+100000);
t=clock()-t;
double time_taken4 = ((double)t)/CLOCKS_PER_SEC;
double pertime4=time_taken4/(double)100000;
cout<<"Time taken to STL's sort 100000 random elements: "<<time_taken4<<" Time per element: "<<pertime4<<endl;
return 0;
}

Output:

The efficiency of selection sort breaks at 1 million elements, for a certain order of elements, it can take more than 10 minutes also.