C++ 代码

blablabla

/
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode father;
* TreeNode(int x) : val(x), left(NULL), right(NULL), father(NULL) {}
* };
/
class Solution {
public:

TreeNode* inorderSuccessor(TreeNode* p) {
    if (p == NULL)
    return NULL;
    if(p->right !=NULL){
        //have right tree
        TreeNode*  pr = p->right;  
        while(pr->left!=NULL){
            pr = pr->left;
        }
        return pr;
    }
    else if (p->father!=NULL &&p->father->left == p  ){
        return p->father;
        //don't have right tree
    }
    else if (p->father!=NULL&&p->father->right == p){
        TreeNode* fa = p -> father;
        while(fa->father != NULL &&fa->father->right == fa){
            fa = fa->father;
        }
        return fa->father;
    }
    else 
        return NULL;
}

};