typedef struct node_ {
        int elt;
        struct node_ *left;
        struct node_ *right;
} node;
typedef node* tree;

tree insert(tree t,int val) {
     tree new;
     if (t==NULL) {
          new = (tree) malloc(sizeof(node));
          new­>elt = val;
          new­>left = NULL;
          new­>right = NULL;
          return new;
     }
     if (val > t­>elt) 
          t­>right = insert(t­>right,val);
     else
          t­>left = insert(t­>left,val);
     return t;
}