What is wrong with my implementation of quicksort? [closed] - c++

Question

Closed. This question needs debugging details. It is not currently accepting answers.
Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem. This will help others answer the question.
Closed 6 years ago.
Improve this question
The program below is for sorting a list using quicksort C++.The code typed below has compiled successfully in code::blocks and in http://cpp.sh/, but unfortunately it hangs after entering in the elements,any help will be appreciated..
void quicksort(vector<int> v,int left_index,int right_index)
{
if(left_index>=right_index)
return;
int pivot=(right_index+left_index)/2;
int left=left_index;
int right=right_index;
while(left<=right)
{
while(v[left]<v[pivot])
left++;
while(v[right]>v[pivot])
right--;
if(left<=right)
{
swap(v,left,right);
left++;right--;
}
}
quicksort(v,left_index,right);
quicksort(v,left,right_index);
}

Answer 1

Passing by reference is must as others have pointed out.
Keep pivot constant during a partition. pivot = v[pivot] ensures that.
outer loop bounds changed to left<=right from left<right.
The running code.
#include <iostream>
#include<vector>
using namespace std;
void print(const vector<int> &v)
{
cout<<"The sorted list is:"<<endl;
for(int i=0;i<(int)v.size();i++)
cout<<v[i]<<' ';
cout<<endl;
}
void swap(vector<int> &v,int left,int right)
{
int temp=v[left];
v[left]=v[right];
v[right]=temp;
}
void quicksort(vector<int> &v,int left_index,int right_index)
{
if(left_index>=right_index)
return;
int pivot=(right_index+left_index)/2;
pivot = v[pivot];
int left=left_index;
int right=right_index;
while(left<right)
{
while(v[left]<=pivot)
left++;
while(v[right]>pivot)
right--;
if(left<right){
swap(v,left,right);
left++;
right--;
}
}
quicksort(v,left_index,right);
quicksort(v,left,right_index);
print(v);
}
int main()
{
int no;
vector<int> v;
cout << "Please enter the elements in your list" << endl;
cout << "Enter 0 to exit..."<<endl;
while(cin >> no)
{
if(no==0)
break;
v.push_back(no);
}
quicksort(v,0,v.size()-1);
return 0;
}