Validate a BST using pointers with golang

validate-bst-with-pointers.go

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func loopBST(root *TreeNode) bool {
    if root == nil {
        return false
    }
    prev := -1
    first := true
    return loop(root, &prev, &first)
}

func loop(leaf *TreeNode, prev *int, first *bool) bool {
    if leaf == nil {
        return true
    }
    
    if !loop(leaf.Left, prev, first) {
        return false
    }
            
    if !*first && leaf.Val <= *prev {
        return false
    }
    
    *first = false
    *prev = leaf.Val
    
    if !loop(leaf.Right, prev, first) {
        return false
    }
    
    return true
}