Use of Recursion

//cheak sorted array or not
#include<iostream>
using namespace std;
bool check(int arr[],int n)
{   if (arr[n-2]==arr[0])
        {return 1;}
    if(arr[n-1]>arr[n-2])
       { return check(arr,n-1) ;}
  else{ return 0;} }

// write the sequence of decnbr
void decnmbr (int n)
{  
  cout<<n<<" ";
   if(n==0){return;}
   decnmbr(n-1);
   }
// find first occurance
int firstoccurance (int a[],int n,int key,int i)
{     if(i>n)
     {return -1;}
    if(a[i]==key)
        {return i;}
        firstoccurance( a,n,key,i+1);
                   }
  //find last occurrence         
  int lstocrnc(int a[],int n,int key,int j)
{   if(j<0){return -1;}
  if(a[j]==key)
     {return j;}
    lstocrnc( a,n,key,j-1);
                   }     
           

int main()
{ int arr[5]={2,3,4,5,6};
  if(check(arr,3))
    {cout << "sorted / increasing order";}
    else {cout<<"Not increasing order ";}
    cout<<endl;
   decnmbr(5);
   int a[7]={1,2,3,5,2,4,2};
    int key;
    cout<<"\nkey =";cin>>key;
    cout<<endl;
   
    int i=0;
    int j=7-1;
    cout << endl;
   cout<< firstoccurance( a,7,key,i)<<endl;
    cout<<lstocrnc(a,7,key,j)<<endl;
    return 0;
}