题解 | #二叉搜索树的第k个节点#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 *	TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 * };
 */
 using namespace std;
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 proot TreeNode类 
     * @param k int整型 
     * @return int整型
     */
    int KthNode(TreeNode* proot, int k) {
        // write code here
        if (!proot) return -1;

        stack<TreeNode*> s;
        TreeNode* p = proot;
        int cnt = 0;
        while (p || !s.empty())
        {
            if (p)
            {
                s.push(p);
                p = p->left;
            }
            else 
            {
                p = s.top();
                s.pop();
                if (++ cnt == k) return p->val;
                p = p->right;
            }
        }
        return -1;
    }
};