lab 4 algorithm

#include<bits/stdc++.h>
using namespace std;

int length = 1 ;

class Heap
{
public:

    Build_MinHeap(int arr[])
    {
        int n = length;
        for(int i=n/2;i>=1;i--)
            Min_heapify(arr,i,n);
    }

    Min_heapify(int arr[],int i,int n)
    {
        int leftchild = 2*i;
        int rightchild = 2*i+1;
        int smaller;

        if(leftchild<=n && arr[leftchild]<arr[i])
            smaller = leftchild;
        else
            smaller = i;

        if(rightchild <=n && arr[rightchild]<arr[smaller])
            smaller = rightchild;

        if(smaller != i)
        {
            swap(arr[smaller],arr[i]);
            Min_heapify(arr,smaller,n);

        }

    }
    void min_heap_insert(int arr[],int key,int n)
    {
        length = n+1;
        arr[n+1] = key;

        heap_change_key(arr,11,key);
    }
    void heap_change_key(int arr[],int i,int key)
    {

        while((i > 1) && arr[i/2] > arr[i])
        {
            swap(arr[i],arr[i/2]);
            i = i/2;
        }
    }
    void display( int arr[])
    {
        for(int i = 1;i<= length;i++)
            cout<<arr[i]<<" ";
        cout<<endl<<endl;
    }




};




int main()
{
    Heap obj;
    freopen("input.txt","r",stdin);
    int arr[100];
    int key;
    cin>>key;
    while(cin)
    {
        cin>>arr[length++];
    }

    length -= 2;



    cout<<"Original Min Heap:"<<endl;
    obj.Build_MinHeap(arr);
    obj.display(arr);

    cout<<"After Insert a value: "<<endl;
    obj.min_heap_insert(arr,key,length);
    obj.display(arr);


    return 0;
}