/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func countNodes(root *TreeNode) int {
if root==nil{
return 0
}
queue := []*TreeNode{root}
count := 0
for len(queue) > 0 {
node := queue[0]
count += 1
queue = queue[1:]
if node.Left != nil {
queue = append(queue, node.Left)
}else{
continue
}
if node.Right != nil {
queue = append(queue, node.Right)
}
}
return count
}