es_1

/*******************************************************************************************/
P-Like
/*******************************************************************************************/
function del_testa(head,elem): nodo
	var head,prec: nodo
	var elem: integer
	begin
	if (head!=NULL) then
        prec=head.link;
        if (head.info=elem) then
            dealloca (head)
            del_testa := del_testa(prec,elem)
        else
            del_testa := head
        endif
    endif
	end

function del_mezzo(head,elem): nodo
	var head,prec: nodo
	var elem: integer
	begin
    if (head!=NULL) then
        prec=head
        head=head.link
        if(head!=NULL) then
            if(head.info==elem) then
                dealloca (head)
                prec.link=head.link
            else
                prec=prec.link
            endif
            del_mezzo:=del_mezzo(prec, elem)
        endif
    endif
	end

function delete_elem(head,elem): nodo
	var head: nodo
	var elem: integer
begin
	head:=del_testa(head,elem)
	head:=del_mezzo(head,elem)
	delete_elem head
end
/*******************************************************************************************/
C++:
/*******************************************************************************************/
nodo* del_testa(nodo* head,int elem){
    if(head){
        nodo* tmp=head->link;
        if(head->info==elem){
            //dealloca head;
            delete head;
            return del_testa(tmp,elem);
        }else{
            return head;
        }

    }
    return NULL; //<- serve per non far impazziare il mio mac,ignora pure.
}

void del_mezzo(nodo* head,int elem){
    if(head){
        nodo* prec=head;
        head=head->link;
        if(head){
            if(head->info==elem){
                delete head;
                prec->link=head->link;
            }else{
                prec=prec->link;
            }
            del_mezzo(prec, elem);
        }
    }
}


/*******************************************************************************************/
Programma completo
/*******************************************************************************************/
#include <iostream>
using namespace std;

struct nodo{
    int info;
    nodo *link;
};

void add(nodo* head,int info){
    if(head->link==NULL){
        nodo* N = new nodo;
        N->info=info;
        N->link=NULL;
        head->link=N;
    }else{
        add(head->link, info);
    }
}

void display(nodo* head){
    while(head){
        cout<<head->info<<" ";
        head=head->link;
    }
    cout<<endl;
}

nodo* del_testa(nodo* head,int elem){
    if(head){
        nodo* tmp=head->link;
        if(head->info==elem){
            //dealloca head;
            delete head;
            return del_testa(tmp,elem);
        }else{
            return head;
        }

    }
    return NULL;
}

void del_mezzo(nodo* head,int elem){
    if(head){
        nodo* prec=head;
        head=head->link;
        if(head){
            if(head->info==elem){
                delete head;
                prec->link=head->link;
            }else{
                prec=prec->link;
            }
            del_mezzo(prec, elem);
        }
    }
}


int main(int argc, const char * argv[]) {
    nodo* P1 = new nodo;
    P1->info=4;
    P1->link=NULL;
    add(P1,4);
    add(P1,2);
    add(P1,4);
    add(P1,4);
    add(P1,2);
    add(P1,4);
    add(P1,4);

    display(P1);
    P1=del_testa(P1,4);
    display(P1);



    cout<<"===="<<endl;
    del_mezzo(P1,4);
    display(P1);
    }