剑指OFFER 二叉树的下一个结点

剑指OFFER 二叉树的下一个结点

/*
struct TreeLinkNode {
    int val;
    struct TreeLinkNode *left;
    struct TreeLinkNode *right;
    struct TreeLinkNode *next;
    TreeLinkNode(int x) :val(x), left(NULL), right(NULL), next(NULL) {
        
    }
};
*/
class Solution {
public:
    TreeLinkNode* target_node = NULL;
    TreeLinkNode* res_node = NULL;
    bool ok = false;
    
    void recur(TreeLinkNode* node)
    {
        if(node == NULL){
            return ;
        }
        recur(node->left);
        if(ok == true){
            res_node = node;
            ok = false;//avoid next entering
        }
        if(node == target_node){
            ok = true;
        }
        recur(node->right);
    }
    
    TreeLinkNode* GetNext(TreeLinkNode* pNode)
    {
        //handle special case
        if(pNode == NULL)return NULL;
        
        //initialize 
        target_node = pNode;
        
        //get root node
        TreeLinkNode* root = pNode;
        while(root->next != NULL){
            root = root->next;
        }
        
        //recurly traverse to find the next node
        recur(root);
        return res_node;
    }
};