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Minimum Absolute Difference in BST

ID: 530; easy

Solution 1

/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
import "math"
func getMinimumDifference(root *TreeNode) int {
result, previous := math.MaxInt16, -1
getMinDiffHelper(root, &result, &previous)
return result
}
func getMinDiffHelper(root *TreeNode, res, prev *int) {
if root == nil {
return
}
getMinDiffHelper(root.Left, res, prev)
if *prev != -1 {
*res = min(*res, abs(root.Val - *prev))
}
*prev = root.Val
getMinDiffHelper(root.Right, res, prev)
}
func min(x, y int) int {
if x > y {
return y
}
return x
}
func abs(x int) int {
if x >= 0 {
return x
}
return -x
}
Keep track of the previous node. Similar to an inorder traversal.