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Commit c1dd1a5

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feat: add golang solution to lcci problems: No. 04.04, 04.05
1 parent 7094659 commit c1dd1a5

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6 files changed

+225
-0
lines changed

6 files changed

+225
-0
lines changed

‎lcci/04.04.Check Balance/README.md‎

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@@ -72,6 +72,42 @@ class Solution {
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}
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```
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### **Go**
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自底向上递归
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```go
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func isBalanced(root *TreeNode) bool {
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return depth(root) >= 0
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}
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func depth(root *TreeNode) int {
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if root == nil {
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return 0
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}
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left := depth(root.Left)
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right := depth(root.Right)
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if left == -1 || right == -1 || abs(left-right) > 1 {
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return -1
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}
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return max(left, right) + 1
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}
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func max(x, y int) int {
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if x > y {
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return x
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}
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return y
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}
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func abs(x int) int {
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if x < 0 {
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return -x
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}
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return x
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}
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```
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### **...**
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```

‎lcci/04.04.Check Balance/README_EN.md‎

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@@ -107,6 +107,42 @@ class Solution {
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}
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```
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### **Go**
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Bottom-up recursion
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```go
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func isBalanced(root *TreeNode) bool {
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return depth(root) >= 0
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}
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func depth(root *TreeNode) int {
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if root == nil {
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return 0
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}
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left := depth(root.Left)
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right := depth(root.Right)
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if left == -1 || right == -1 || abs(left-right) > 1 {
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return -1
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}
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return max(left, right) + 1
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}
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func max(x, y int) int {
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if x > y {
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return x
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}
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return y
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}
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func abs(x int) int {
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if x < 0 {
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return -x
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}
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return x
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}
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```
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### **...**
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```

‎lcci/04.04.Check Balance/Solution.go‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,29 @@
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func isBalanced(root *TreeNode) bool {
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return depth(root) >= 0
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}
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func depth(root *TreeNode) int {
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if root == nil {
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return 0
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}
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left := depth(root.Left)
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right := depth(root.Right)
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if left == -1 || right == -1 || abs(left-right) > 1 {
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return -1
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}
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return max(left, right) + 1
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}
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func max(x, y int) int {
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if x > y {
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return x
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}
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return y
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}
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func abs(x int) int {
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if x < 0 {
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return -x
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}
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return x
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}

‎lcci/04.05.Legal Binary Search Tree/README.md‎

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Original file line numberDiff line numberDiff line change
@@ -83,6 +83,51 @@ class Solution {
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}
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```
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### **Go**
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- 非递归中序遍历
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```go
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func isValidBST(root *TreeNode) bool {
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stack := make([]*TreeNode, 0)
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var prev *TreeNode = nil
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node := root
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for len(stack) > 0 || node != nil {
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for node != nil {
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stack = append(stack, node)
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node = node.Left
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}
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node = stack[len(stack)-1]
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stack = stack[:len(stack)-1]
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if prev == nil || node.Val > prev.Val {
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prev = node
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} else {
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return false
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}
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node = node.Right
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}
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return true
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}
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```
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- 利用上界下界判定
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```go
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func isValidBST(root *TreeNode) bool {
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return check(root, math.MinInt64, math.MaxInt64)
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}
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func check(node *TreeNode, lower, upper int) bool {
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if node == nil {
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return true
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}
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if node.Val <= lower || node.Val >= upper {
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return false
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}
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return check(node.Left, lower, node.Val) && check(node.Right, node.Val, upper)
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}
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```
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### **...**
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```

‎lcci/04.05.Legal Binary Search Tree/README_EN.md‎

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Original file line numberDiff line numberDiff line change
@@ -112,6 +112,51 @@ class Solution {
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}
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```
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### **Go**
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- Non-recursive in-order traversal
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```go
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func isValidBST(root *TreeNode) bool {
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stack := make([]*TreeNode, 0)
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var prev *TreeNode = nil
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node := root
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for len(stack) > 0 || node != nil {
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for node != nil {
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stack = append(stack, node)
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node = node.Left
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}
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node = stack[len(stack)-1]
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stack = stack[:len(stack)-1]
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if prev == nil || node.Val > prev.Val {
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prev = node
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} else {
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return false
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}
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node = node.Right
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}
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return true
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}
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```
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- Use upper bound and lower bound to check
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```go
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func isValidBST(root *TreeNode) bool {
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return check(root, math.MinInt64, math.MaxInt64)
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}
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func check(node *TreeNode, lower, upper int) bool {
150+
if node == nil {
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return true
152+
}
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if node.Val <= lower || node.Val >= upper {
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return false
155+
}
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return check(node.Left, lower, node.Val) && check(node.Right, node.Val, upper)
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}
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```
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### **...**
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```
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Original file line numberDiff line numberDiff line change
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func isValidBST(root *TreeNode) bool {
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return check(root, math.MinInt64, math.MaxInt64)
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}
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func check(node *TreeNode, lower, upper int) bool {
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if node == nil {
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return true
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}
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if node.Val <= lower || node.Val >= upper {
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return false
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}
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return check(node.Left, lower, node.Val) && check(node.Right, node.Val, upper)
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}
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// func isValidBST(root *TreeNode) bool {
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// stack := make([]*TreeNode, 0)
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// var prev *TreeNode = nil
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// node := root
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// for len(stack) > 0 || node != nil {
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// for node != nil {
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// stack = append(stack, node)
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// node = node.Left
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// }
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// node = stack[len(stack)-1]
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// stack = stack[:len(stack)-1]
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// if prev == nil || node.Val > prev.Val {
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// prev = node
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// } else {
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// return false
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// }
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// node = node.Right
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// }
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// return true
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// }

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