list.cc

#include <stdio.h>

template  <typename T>
class list
{
  struct node {
    node *next;
    node *prev;
    T val;
  };
  node* head;
  
public:
  list() 
  {
    head = NULL;
  };
  void insert(T e) 
  {
    node* n = new node();
    n->val = e;
    n->next = head;
    if (head!=NULL) {
      head->prev = n;
    }
    n->prev=NULL;
    head = n;
  };

  void del(T e)
  {
    node *x = head;
    while (x) {
      if (e == x->val) {
	if (x->next!=NULL) {
	  x->next->prev = x->prev;
	}
	if (x->prev!=NULL) {
	  x->prev->next = x->next;

	}
	else {
	  head = x->next;
	}
      }
      x = x->next;
    }
  }
  node* find(T e) 
  {
    node* x = head;
    while (x) {
      if (e==x->val) {
	return x;
      }
      x = x->next;
    }
    return NULL;
  }
  void print() 
  {
    node *x = head;
    while(x) {
      printf("%d",x->val);
      x = x->next;
    }
  }
};

int main() {
  list<char> l;
  l.insert('a');  
  l.print();
  l.del('a');
  l.print();
  l.insert('a');  
  l.print();
  l.insert('b');  
  l.print();
  l.del('a');
  return 0;
}