70. 二叉搜索树的第k个结点 --中序遍历

class Solution {
public:
    
    TreeNode *ans;
    
    TreeNode* kthNode(TreeNode* root, int k) {
        cout<<"主函数"<<" "<<"root="<<root->val<<endl;
        dfs(root,k);
       // cout<<"主函数"<<" "<<"root="<<root->val<<endl;
        return ans;
    }
    
    void dfs(TreeNode* root, int &k)
    {
        cout<<"递归"<<endl;
        if(!root) {
            cout<<"满足if(!root)"<<endl;
            return;
        }
        cout<<"root="<<root->val<<endl;
        dfs(root->left, k);
        cout<<"k="<<k<<" "<<endl;
        k--;
        cout<<"执行k--后，k值="<<k<<" "<<endl;
        if(!k){
            ans =root;
            cout<<"满足if(!k)"<<endl;
        }
        if(k > 0) {
            cout<< "满足if(k>0)"<<endl;
            dfs(root->right,k);
        }
    }
};