题解 | #二叉树的中序遍历#

中序遍历：左-根-右

/**
 * 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> inorderTraversal(TreeNode* root) {
        // write code here
        vector<int> res;
        if (root == NULL) return res;
        vector<TreeNode*> stack;
        TreeNode* tmp = root;
        stack.push_back(root);
        do {
            tmp = stack.back();
            if (tmp->left) {
                stack.push_back(tmp->left);
                tmp->left = NULL;
                continue;
            }
            stack.pop_back();
            res.push_back(tmp->val);
            if (tmp->right) {
                stack.push_back(tmp->right);
            }

        } while (!stack.empty());
        return res;
    }
};