README_EN.md

285. Inorder Successor in BST

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Description

Given the root of a binary search tree and a node p in it, return the in-order successor of that node in the BST. If the given node has no in-order successor in the tree, return null.

The successor of a node p is the node with the smallest key greater than p.val.

 

Example 1:

Input: root = [2,1,3], p = 1
Output: 2
Explanation: 1's in-order successor node is 2. Note that both p and the return value is of TreeNode type.

Example 2:

Input: root = [5,3,6,2,4,null,null,1], p = 6
Output: null
Explanation: There is no in-order successor of the current node, so the answer is null.

 

Constraints:

• The number of nodes in the tree is in the range [1, 104].
• -105 <= Node.val <= 105
• All Nodes will have unique values.

Solutions

Python3

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None


class Solution:
    def inorderSuccessor(self, root: 'TreeNode', p: 'TreeNode') -> 'TreeNode':
        cur, ans = root, None
        while cur:
            if cur.val <= p.val:
                cur = cur.right
            else:
                ans = cur
                cur = cur.left
        return ans

Java

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode inorderSuccessor(TreeNode root, TreeNode p) {
        TreeNode cur = root, ans = null;
        while (cur != null) {
            if (cur.val <= p.val) {
                cur = cur.right;
            } else {
                ans = cur;
                cur = cur.left;
            }
        }
        return ans;
    }
}

Go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func inorderSuccessor(root *TreeNode, p *TreeNode) (ans *TreeNode) {
	cur := root
	for cur != nil {
		if cur.Val <= p.Val {
			cur = cur.Right
		} else {
			ans = cur
			cur = cur.Left
		}
	}
	return
}

C++

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* inorderSuccessor(TreeNode* root, TreeNode* p) {
        TreeNode *cur = root, *ans = nullptr;
        while (cur != nullptr) {
            if (cur->val <= p->val) {
                cur = cur->right;
            } else {
                ans = cur;
                cur = cur->left;
            }
        }
        return ans;
    }
};

JavaScript

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {TreeNode} p
 * @return {TreeNode}
 */
var inorderSuccessor = function (root, p) {
    let cur = root;
    let ans = null;
    while (cur != null) {
        if (cur.val <= p.val) {
            cur = cur.right;
        } else {
            ans = cur;
            cur = cur.left;
        }
    }
    return ans;
};

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