```
#include <bits/stdc++.h>
using namespace std;
struct node {
int val;
node* left;
node* right;
node() : val(-1),left(nullptr),right(nullptr) {}
node(int v) : val(v),left(nullptr),right(nullptr) {}
};
class tree {
stack<node*> s;
node* root;
public:
tree(node* root) {
root->val = 5;
node* l = new node(4);
node* r = new node(6);
node* ll = new node(1);
node* rr = new node(2);
root->left = l,root->right = r,l->left = ll,l->right = rr;
this->root = root;
}
node* nxt() {
while(root) {
s.push(root);
root = root->left;
}
if(s.empty()) return nullptr;
node* tp = s.top();
s.pop();
if(tp->right) s.push(tp->right);
return tp;
}
};
int main() {
node* t = new node();
tree* test = new tree(t);
cout << test->nxt()->val << '\n'; // 1
cout << test->nxt()->val << '\n'; // 4
cout << test->nxt()->val << '\n'; // 2
cout << test->nxt()->val << '\n'; // 5
cout << test->nxt()->val << '\n'; // 6
return 0;
}
```
代码复盘
