树的遍历 递归与非递归实现

void preorder(Tree *tree){
    if(t==NULL){
        return;
    }
    cout<<tree->val<<endl;
    preorder(tree->left);
    preorder(tree->right);
}


void inorder(Tree *tree){
    if(tree==NULL){
        return;
    }
    inorder(tree->left);
    cout<<tree->val;
    inorder(tree->right);
}

void lastorder (Tree *tree){
    if (tree== NULL){
        return;
    }
    lastorder(tree->left);
    lastorder(tree->right);
    cout<<tree->val;
}

void preorder( Tree *tree){
    stack<Tree *> s;
    while(tree != NULL || (!s.empty())){
        if(tree!=NULL){
            cout<<tree->val<<endl;
            s.push(tree);
            tree = tree->left;
        }else{
            tree = s.top();
            s.pop();
            tree = tree->right;
        }
    }
}

void inorder(Tree* tree){
    stack<Tree*>s;
    while(tree!=NULL || !s.empty()){
        if (tree!=NULL){
            s.push(tree);
            tree = tree->left();
        } else{
            tree =s.top();
            s.pop();
            cout<<tree->val;
            tree = tree->right;
        }

    }
}

void lastvisit(Tree *tree){
    stack<int> s;
    Tree * last = root;
    while (tree!=NULL || !s.empty()){
        if(tree!=NULL){
            s.push(tree);
            tree = tree->left;
        } else if( tree->right ==NULL || last == tree->right){
            tree = s.top();
            cout<<tree->val<<endl;
            last = tree;
            tree =NULL;
        } else{
            tree = tree->right;
        }
        
    }

}

https://blog.csdn.net/zhhp1001/article/details/88257018?depth_1-utm_source=distribute.pc_relevant.none-task&utm_source=distribute.pc_relevant.none-task