c_cpp 144.二叉树预订遍历

Posted 2021-05-14

//Runtime: 0 ms, faster than 100.00%

#include <ios>
static auto fastInput = []() {
    ios_base::sync_with_stdio(false),cin.tie(nullptr);
    return 0;
}();

class Solution {
public:
    vector<int> array;
    
    vector<int> preorderTraversal(TreeNode* root) {
        travelTree(root);       
        return array;
    }
    
    void travelTree(TreeNode* root){
        if(root){
            array.push_back(root->val);
            travelTree(root->left);
            travelTree(root->right);
        }
    }
};

class Solution {
public:
    vector<int> preorderTraversal(TreeNode* root) {
        if(!root) return vector<int>();
        
        vector<int> result;
        stack<TreeNode*> treeStack;
        treeStack.push(root);
        
        while(!treeStack.empty()){
            TreeNode* temp = treeStack.top();
            result.push_back(temp->val);
            treeStack.pop();
            if(temp->right)
                treeStack.push(temp->right);
            if(temp->left)
                treeStack.push(temp->left);
        }
        return result;
    }
};