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783.cpp
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783.cpp
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/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
int prev = -1;
int curr = -1;
int res = INT_MAX;
void dfs(TreeNode* node) {
if (node == nullptr) return;
dfs(node->left);
prev = curr;
curr = node->val;
if (prev != -1) {
res = min(res, curr - prev);
}
dfs(node->right);
}
int minDiffInBST(TreeNode* root) {
dfs(root);
return res;
}
};
// v2
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode() : val(0), left(nullptr), right(nullptr) {}
* TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
* TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
* };
*/
class Solution {
public:
int res = INT_MAX;
int minVal = INT_MIN / 2;
void preorder(TreeNode* node) {
if (!node) return;
preorder(node->left);
res = min(res, node->val - minVal);
minVal = node->val;
preorder(node->right);
}
int minDiffInBST(TreeNode* root) {
preorder(root);
return res;
}
};