CODEWITHSUNDEEP
c++
Baz
Baz

Reputation: 13123

"Insert before" for std::list

Lets say I have a linked list which contains the following:

1, 2, 4, 5, 6, 2, 3, 2

now lets say I wish to convert this to:

1, 10, 2, 4, 5, 6, 10, 2, 3, 10, 2

i.e. insert 10 before all 2's.

How should I do this?

Upvotes: 3

Views: 5580

Answers (4)

Minion91
Minion91

Reputation: 1929

while(item != NULL)
{
if(item->intval == 2)
{
Item *newitem = (Item *) malloc(sizeof(Item));
newitem->intval = 10;
prev->next = newitem;
newitem->next = item;
}
prev = item;
item = item->next;
}

If you made your own linked list. Also off the top of my head, and c style.

Upvotes: -1

Rahul Razdan
Rahul Razdan

Reputation: 429

create a structure with node and info like 

struct test{

int info;
int *node;

}

you can refer them as test->info and test->node

now try something like this .

while(end_of_list){

list[index]=2;

create a new structure object(new_struct) .

new_struct->info=10;
new_struct->node=node_containing_2.

previous_node_to_2->node=new_struct.

}

Upvotes: 0

Some programmer dude
Some programmer dude

Reputation: 409166

Maybe something like this:

auto it = l.begin();
while ((it = std::find(it, l.end(), 2)) != l.end())
{
    it = l.insert(it, 10);
    std::advance(it, 2);
}

Upvotes: 1

john
john

Reputation: 8027

Off the top of my head

for (std::list<int>::iterator i = l.begin(); i != l.end(); ++i)
  if (*i == 2)
     l.insert(i, 10);

Simple enough. You don't need to worry about iterator invalidation because insert on a std::list does not invalidate any iterators. It's one of the advantages of using std::list.

Upvotes: 9

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