LeetCode 144. Binary Tree Preorder Traversal 动态演示

先序遍历的非递归办法，还是要用到一个stack

class Solution {
public:
    vector<int> preorderTraversal(TreeNode* root) {
        vector<int> ret;
        if(!root)
            return ret;
        stack<TreeNode*> stk;
        stk.push(root);
        //ahd(root)
        //a(stk)
        //a(ret)
        while(stk.size()>){
            TreeNode* cur=stk.top(); stk.pop();
            //a(cur)
            //lk("root", cur)
            ret.push_back(cur->val);
            //dsp
            if(cur->right) stk.push(cur->right);
            if(cur->left) stk.push(cur->left);
            //dsp
        }
 
        return ret;
    }
};

程序运行动态演示：http://simpledsp.com/FS/Html/lc144.html