feat: add swift implementation to lcci problem: No.04.05 #2657

Original file line number	Diff line number	Diff line change
Expand Up		@@ -291,6 +291,47 @@ public class Solution {
		}
		```

	```swift
	/* class TreeNode {
	* var val: Int
	* var left: TreeNode?
	* var right: TreeNode?
	*
	* init(_ val: Int) {
	* self.val = val
	* self.left = nil
	* self.right = nil
	* }
	* }
	*/

	class Solution {
	private var prev: TreeNode?

	func isValidBST(_ root: TreeNode?) -> Bool {
	return dfs(root)
	}

	private func dfs(_ root: TreeNode?) -> Bool {
	guard let root = root else {
	return true
	}

	if !dfs(root.left) {
	return false
	}

	if let prev = prev, prev.val >= root.val {
	return false
	}

	prev = root

	return dfs(root.right)
	}
	}
	```

		<!-- tabs:end -->

		<!-- end -->

41 changes: 41 additions & 0 deletions lcci/04.05.Legal Binary Search Tree/README_EN.md

Show comments View file Open in desktop

Original file line number	Diff line number	Diff line change
Expand Up		@@ -328,6 +328,47 @@ public class Solution {
		}
		```

	```swift
	/* class TreeNode {
	* var val: Int
	* var left: TreeNode?
	* var right: TreeNode?
	*
	* init(_ val: Int) {
	* self.val = val
	* self.left = nil
	* self.right = nil
	* }
	* }
	*/

	class Solution {
	private var prev: TreeNode?

	func isValidBST(_ root: TreeNode?) -> Bool {
	return dfs(root)
	}

	private func dfs(_ root: TreeNode?) -> Bool {
	guard let root = root else {
	return true
	}

	if !dfs(root.left) {
	return false
	}

	if let prev = prev, prev.val >= root.val {
	return false
	}

	prev = root

	return dfs(root.right)
	}
	}
	```

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		<!-- end -->

38 changes: 38 additions & 0 deletions lcci/04.05.Legal Binary Search Tree/Solution.swift

Show comments View file Open in desktop

Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,38 @@
	/* class TreeNode {
	* var val: Int
	* var left: TreeNode?
	* var right: TreeNode?
	*
	* init(_ val: Int) {
	* self.val = val
	* self.left = nil
	* self.right = nil
	* }
	* }
	*/

	class Solution {
	private var prev: TreeNode?

	func isValidBST(_ root: TreeNode?) -> Bool {
	return dfs(root)
	}

	private func dfs(_ root: TreeNode?) -> Bool {
	guard let root = root else {
	return true
	}

	if !dfs(root.left) {
	return false
	}

	if let prev = prev, prev.val >= root.val {
	return false
	}

	prev = root

	return dfs(root.right)
	}
	}

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