Problem
Analysis Process
Recursive solution is very easy
we need to use iterative algorithm
Here we are going to use the auxiliary stack
1.The left subtree is traversed first to push the element onto the stack and then traversed in order to push the element out of the stack
2.Then go to the right node and do the same for the right subtree
Code
Recursive solution
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
var res []int
func inorderTraversal(root *TreeNode) []int {
res = make([]int, 0)
dfs(root)
return res
}
func dfs(root *TreeNode) {
if root != nil {
dfs(root.Left)
res = append(res, root.Val)
dfs(root.Right)
}
}
Iterative solution
/**
* Definition for a binary tree node.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func inorderTraversal(root *TreeNode) []int {
var res []int
var stack []*TreeNode //make a stack
for 0 < len(stack) || root != nil { //root != nil is ued to determine for once must be put in the end
for root != nil {
stack = append(stack, root) //push
root = root.Left // move to the left
}
index := len(stack) - 1 //Top
res = append(res, stack[index].Val) //inorder traversal to pop
root = stack[index].Right //right node is continued to be pushed
stack = stack[:index] //pop
}
return res
}