搜索二叉树变换为双向链表

 

TreeNode* Convert(TreeNode* pRootOfTree)

    {

        if(pRootOfTree == nullptr) return nullptr;

        TreeNode* pre = nullptr;

         

        convertHelper(pRootOfTree, pre);

         

        TreeNode* res = pRootOfTree;

        while(res ->left)

            res = res ->left;

        return res;

    }

     

    void convertHelper(TreeNode* cur, TreeNode*& pre)

    {

        if(cur == nullptr) return;

         

        convertHelper(cur ->left, pre);

         

        cur ->left = pre;

        if(pre) pre ->right = cur;

        pre = cur;

         

        convertHelper(cur ->right, pre);         

    }




--------------------------------------------------------------------------------------------------

class Solution {
public:
    TreeNode* Convert(TreeNode* pRootOfTree)
    {
        if(!pRootOfTree) return NULL;
        TreeNode* pre=NULL;
        ConvertHelp(pRootOfTree,pre);
        TreeNode* res=pRootOfTree;
        while(res->left)
            res=res->left;
        return res;
    }
private:
    void ConvertHelp(TreeNode* cur,TreeNode* &pre)
    {
        if(!cur) return;
        ConvertHelp(cur->left,pre);
        cur->left=pre;
        if(pre) pre->right=cur;
        pre=cur;
        ConvertHelp(cur->right,pre);
    }
    
};