783. Minimum Distance Between BST Nodes
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Given a Binary Search Tree (BST) with the root node root
, return the minimum difference between the values of any two different nodes in the tree.
Example :
Input: root = [4,2,6,1,3,null,null] Output: 1 Explanation: Note that root is a TreeNode object, not an array. The given tree [4,2,6,1,3,null,null] is represented by the following diagram: 4 / 2 6 / 1 3 while the minimum difference in this tree is 1, it occurs between node 1 and node 2, also between node 3 and node 2.
Note:
- The size of the BST will be between 2 and
100
. - The BST is always valid, each node‘s value is an integer, and each node‘s value is different.
Approach #1: 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: int minDiffInBST(TreeNode* root) { solve(root); sort(nodes.begin(), nodes.end()); int minNum = INT_MAX; for (int i = 1; i < nodes.size(); ++i) { minNum = min(minNum, nodes[i]-nodes[i-1]); } return minNum; } void solve(TreeNode* root) { if (root->left != NULL) minDiffInBST(root->left); nodes.push_back(root->val); if (root->right != NULL) minDiffInBST(root->right); } private: vector<int> nodes; };
Approach #2: Java. [Inorder travel]
/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { Integer minDiff = Integer.MAX_VALUE, pre = null; public int minDiffInBST(TreeNode root) { if (root.left != null) minDiffInBST(root.left); if (pre != null) minDiff = Math.min(minDiff, root.val-pre); pre = root.val; if (root.right != null) minDiffInBST(root.right); return minDiff; } }
Approach #3: Python.
# Definition for a binary tree node. # class TreeNode(object): # def __init__(self, x): # self.val = x # self.left = None # self.right = None class Solution(object): minDiff = float(‘inf‘) pre = -float(‘inf‘) def minDiffInBST(self, root): """ :type root: TreeNode :rtype: int """ if root.left != None: self.minDiffInBST(root.left) self.minDiff = min(self.minDiff, root.val-self.pre) self.pre = root.val if root.right != None: self.minDiffInBST(root.right) return self.minDiff;
Notes:
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