leetcode-go/easy/530.minimum-absolute-difference-in-bst.go

var pre int = 0
var ini bool = false

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func getMinimumDifference(root *TreeNode) (diff int) {
	pre, diff = 0, 1<<32-1
	ini = false
	inorder(root, &diff)
	return
}

func inorder(root *TreeNode, diff *int) {
	if root == nil {
		return
	}
	inorder(root.Left, diff)
	if ini {
		d := abs(root.Val - pre)
		if d < *diff {
			*diff = d
		}
	} else {
		ini = true
	}
	pre = root.Val
	inorder(root.Right, diff)
}

func abs(x int) int {
	if x < 0 {
		return -x
	}
	return x
}