剑指offer 编程题（59）：二叉搜索树的第k个结点

/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};
*/
class Solution {
public:
vector<TreeNode*> res;
void inOrder(TreeNode * root)
{
if (root == NULL)
{
return;
}
inOrder(root->left);
res.push_back(root);
inOrder(root->right);
}
TreeNode* KthNode(TreeNode* pRoot, int k)
{
if(!pRoot)
return pRoot;
inOrder(pRoot);
if(res.size() < k || k <= 0)
{
return NULL;
}
return res[k - 1];
}
};

class Solution {
public:
int count = 0;
TreeNode *res = NULL;
void inOrder(TreeNode * root,int k)
{
if (root == NULL)
{
return;
}
inOrder(root->left,k);
count++;
if(count == k)
{
res = root;
}
inOrder(root->right,k);
}
TreeNode* KthNode(TreeNode* pRoot, int k)
{
if(!pRoot)
return pRoot;
inOrder(pRoot,k);

return res;
}
};