Leecode笔记-中序遍历

</pre><pre name="code" class="cpp">/**中序遍历
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    vector<int> inorderTraversal(TreeNode* root) {
        TreeNode *p;
        p=root;
        vector<int> a;
        stack<TreeNode *> s;
        if(root==NULL) return a;
        while(!s.empty()||p!=NULL)
        {
            while(p!=NULL)
            {
                s.push(p);
                p=p->left;//找到树最左边的叶子，这时的p相当于根节点
            }
            p=s.top();
            a.push_back(p->val);//输出
            s.pop();//弹出
            p=p->right;//根节点访问完了，访问右孩子
        }
        return a;
    }
};

/*vector<int> ret;
        stack<TreeNode *> s;
        TreeNode *temp = root;

        while (!s.empty() || temp != NULL)
        {
            while (temp != NULL)
            {
                s.push(temp);
                temp = temp->left;
            }

            temp = s.top();
            ret.push_back(temp->val);
            s.pop();
            temp = temp->right;
        }

        return ret;
    }