task 3( ds lab 5) 3rd sem

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

int heap_size;

int left(int i)
{
    return 2*i;
}
int right(int i)
{
    return 2*i+1;
}
int parent(int i)
{
    return i/2;
}
void min_heapify(int A[],int i)
{
    int l,r,smallest;
    l=left(i);
    r=right(i);

    if(l<=heap_size && A[l]<A[i])
        smallest=l;
    else
        smallest=i;

    if(r<=heap_size && A[r]<A[smallest])
        smallest=r;

    if(smallest!=i)
    {
        swap(A[i],A[smallest]);
        min_heapify(A,smallest);
    }

}
void build_min_heap(int h[])
{
    for(int i=heap_size/2; i>0; i--)
        min_heapify(h,i);
}
int heap_min(int h[])
{
    return h[1];
}
int heap_extract_min(int h[])
{
    int mn;
    if(heap_size<=0)
        cout<<"Underflow"<<endl;
    else
    {
        mn=h[1];
        h[1]=h[heap_size];
        heap_size--;
        min_heapify(h,1);
        return mn;
    }
    build_min_heap(h);
}
void heap_decrease_key(int h[],int i, int key)
{
    if(h[i]<key)
    {
        cout<<"ERROR";
        return;
    }
    else
    {
        h[i]=key;
        while(i>1&&h[parent(i)]>h[i])
        {
            swap(h[i],h[parent(i)]);
            i=parent(i);
        }

    }
build_min_heap(h);
}
void display(int h[])
{
    for(int i=1; i<=heap_size; i++)
        cout<<h[i]<<" ";
}

int main()
{
    int h[100];
    cin>>heap_size;
    for(int i=1; i<=heap_size; i++)
    {
        cin>>h[i];
    }
    build_min_heap(h);
    cout<<"MIN HEAP is"<<endl;
    display(h);
    heap_decrease_key(h,2,1);
    cout<<"\nHeap decreased key"<<endl;
    display(h);
    heap_extract_min(h);
    cout<<"\nMin extracted"<<endl;
    display(h);
}