I have a 

```
typedef struct node
{
   node* br;
   node* son;
};

```

Given a string `char* str` which consits of sequence of `(`,`)`
I need to build a tree,for this string ,for example :
for string (()())() the following tree will be built:

```
       br        br 
node ----- node ---- NULL
    |son    |son
    |      NULL
    |   br        br      br
   node --- node --- node --- NULL
           |son   |son
          NULL   NULL

```