linked list debugging (delete C++ keyword is mysterious)? -

i trying solve problem: delete node singly linked list give pointer node. approach overwrite data of next element in list onto current element of list.

in code below, have 2 versions of deleting code: deletenode , deletenode2.

void deletenode(node * x) {  while(x->next != null){     x->data = x->next->data;     x = x->next; }  delete x; x=null;  }  void deletenode2(node * x) {  while(x->next->next != null){      x->data = x->next->data;     x = x->next;  }   x->data = x->next->data; delete x->next; x->next=null;  } 

i initialized list with: 1,2,3,4,5 , tried delete node 3. deletenode output is: 1,2,4,5,0 while deletenode2: 1,2,4,5

also when remove "x->next=null" line deletenode2 has same output 1. question is, how delete statement work in c++? set bits in pointed address 0?

for deletenode(..), x pointer has been deleted not appropriately been set null because prints 0 instead of skipping it. deletenode2, statement "x->next=null" equivalent "x=null" in deletenode since both pointers conceptually point same address, don't have same effect?

the rest of code shown below:

#include<iostream> #include<stdlib.h>  using namespace std;  class node { public:  int data; node * next;  node ( int ) {     data = ;        next = null;      }  };  bool appendtotail ( node * ptr, int ){    while (ptr->next != null)   ptr = ptr->next;    if (ptr==null) {       return false;    }  else {     ptr->next = new node(a);  }  }  void printlist (node * head) {   while (head!=null){       cout<<head->data<<endl;      head = head->next;  }  }  int main(void) {  node * head; head = new node(1); appendtotail(head,2);  appendtotail(head,3); appendtotail(head,4); appendtotail(head,5);  node * = head->next->next;  printlist(head); cout<<"removed:"<<endl;  deletenode2(i);  printlist(head);      return 0;  } 

your answer why x doesn't change can demonstrated simpler program:

#include <iostream>  void foo(int x) {    x = 10;  // change 10 }  int main() {    int num = 4;    foo(num);    std::cout << num; // num still 4!  why? } 

so why num still 4? why didn't value change 10? "pass-by-value", because you're doing in pointer code.

you should either passing pointer reference, or pointer pointer (if need further explanation, fix example above make num equal 10 on return foo).