LeetCode590. N叉树的后序遍历

题目

class Solution {
public:
    vector<int>ans;
    vector<int> postorder(Node* root) {
        dfs(root);
        return ans;
    }
    void dfs(Node* root){
        if(root == NULL) return;
        for(int i = 0;i < root->children.size();i++){
            dfs(root->children[i]);
        }
        ans.push_back(root->val);
    }
};

class Solution {
public:
    
    vector<int> postorder(Node* root) {
        vector<int>ans;
        stack<Node*>s;
        s.push(root);
        while(!s.empty()){
            Node* node = s.top();s.pop();
            if(node) ans.push_back(node->val);
            else continue;

            for(int i = 0;i<node->children.size();i++)
                s.push(node->children[i]);
        }
        reverse(ans.begin(),ans.end());return ans;
    }
    
};