144.二叉树的前序遍历

两天宇宙人

2020-02-20

😂

class Solution {
public:
    vector<int> preorderTraversal(TreeNode* root) {
        vector<int> vec;
        stack<TreeNode* > stk;
        if(root)
            stk.push(root);
        while(stk.size()) {
            auto top = stk.top();
            stk.pop();
            if(top->right) {
                stk.push(top->right);
            }
            vec.push_back(top->val);
            if(top->left) {
                stk.push(top->left);
            } 
              
        }
        return vec;
    }
};