剑指Offer15

class Solution {
public:
    vector> res;
    vector tmp;
    vector> pathSum(TreeNode* root, int target) {
        if(!root){
            return res;
        }else
        {
            dfs(root, target);
        }
        return res;
    }
    void dfs(TreeNode* node, int target)
    {
        target -= node->val;
        tmp.push_back(node->val);
        if(node->left != nullptr){
            dfs(node->left, target);
        }
        if(node->right != nullptr){
            dfs(node->right, target);
        }
        if(node->left == nullptr && node->right == nullptr && target == 0){
            res.push_back(tmp);
        }
        tmp.pop_back();
    }
};

class Solution {
public:
    
    Node* treeToDoublyList(Node* root) {
        if(root == nullptr)
        {
            return nullptr;
        }
        inorder(root);
        head->left = pre;
        pre->right = head;
        return head;
    }
private:
    Node  *pre, *head;
    void inorder(Node* cur)
    {
        if(cur == nullptr){
            return;
        }
        inorder(cur->left);
        if(pre != nullptr)
        {
            pre->right = cur;
        }
        else 
        {
            head = cur;
        }
        cur->left = pre;
        pre = cur;
        inorder(cur->right);
    }
};

class Solution {
public:
    int kthLargest(TreeNode* root, int k) {
        inorder(root, k);
        return res;
    }
    void inorder(TreeNode* root, int& k)
    {
        if(root == nullptr)
        {
            return;
        }
        inorder(root->right, k);
        if(k == 0){
            return;
        }
        if(--k == 0){
            res = root->val;
        }
        inorder(root->left, k);
    }
private:
    int res;
};