题解 | 二叉树的前序遍历

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
class Solution {
public:
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 
     * @param root TreeNode类 
     * @return int整型vector
     */
    vector<int> preorderTraversal(TreeNode* root) {
        // write code here
        vector<int> res;
        if(!root) return res;
        stack<TreeNode*> s;
        s.push(root);
        while(!s.empty()){
            TreeNode* node=s.top();
            s.pop();
            res.push_back(node->val);
            if(node->right){s.push(node->right);}
            if(node->left){s.push(node->left);}
        }
        return res;
    }
};