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# 530 Minimum Absolute Difference in BST

Given a binary search tree with non-negative values, find the minimum [absolute difference](https://en.wikipedia.org/wiki/Absolute_difference) between values of any two nodes.

**Example:**

```
Input:


   1
    \
     3
    /
   2


Output:

1


Explanation:

The minimum absolute difference is 1, which is the difference between 2 and 1 (or between 2 and 3).
```

**Note:**There are at least two nodes in this BST.

**Complexity**: O(n) time O(N) space

**The Idea**: If we run an in order traversal through the tree, the minimum difference is guaranteed to be between two adjacent elements. So that is what we do while maintaining the minimum value.

```cpp
int getMinimumDifference(TreeNode* root) {
    int prev = INT_MAX, my_min = INT_MAX;
    getMinimumDifferenceRec(root, prev, my_min);
    return my_min;
}

void getMinimumDifferenceRec(TreeNode* root, int &prev, int &my_min) {
    if (root) {
        getMinimumDifferenceRec(root->left, prev, my_min);
        my_min = min(my_min, abs(root->val - prev));
        prev = root->val;
        getMinimumDifferenceRec(root->right, prev, my_min);
    }
}
```