Why test cases 3 and 4 wrong

#1

#include
#include
#include
using namespace std;
struct node{
int data;
node* left;
node* right;
};
int sum=0;
node* buildbst(node *root){
int d;
cin>>d;
if(root==NULL){
root =new node;
root->data=d;
root->left=NULL;
root->right=NULL;
}
string str1,str2;
cin>>str1;
if(str1==“true”){
root->left=buildbst(root->left);
cin>>str2;
if(str2==“true”){
root->right=buildbst(root->right);
}
else{
root->left=NULL;
root->right=NULL;
}

}
else{
cin>>str2;
if(str2==“true”){
root->right=buildbst(root->right);
}
else{
root->left=NULL;
root->right=NULL;
}

}
return root;
}
void zigzag(node root){
stack<node>s1;
stack<node*>s2;
s1.push(root);

while(s1.size()||s2.size()){
    while(s1.size()){
        node *w=s1.top();
        cout<<w->data<<" ";
        s1.pop();
		if(w->left){
        s2.push(w->left);}
		if(w->right){
        s2.push(w->right);}
    }
    while(s2.size()){
        node *s=s2.top();
        cout<<s->data<<" ";
        s2.pop();
		if(s->right){
        s1.push(s->right);}
		if(s->left){
        s1.push(s->left);}
    }
    
    
}

}

int main() {
node* root=NULL;
root= buildbst(root);

    zigzag(root);
	return 0;

}

#2

Hey @dineshjani
There’s a problem with your buildBST function, the correct code for the function should be:

node* buildbst(node *root){
int d;
cin>>d;
if(root==NULL){
root =new node;
root->data=d;
root->left=NULL;
root->right=NULL;
}
string str1,str2;
cin>>str1;

if(str1=="true"){
root->left=buildbst(root->left);
}
else root->left = NULL;
cin>>str2;

if(str2=="true"){
root->right=buildbst(root->right);
}
else root->right = NULL;

return root;
}