Merge pull request youngyangyang04#992 from qxuewei/master

添加 102.二叉树的层序遍历 Swift版本

Author: youngyangyang04

Diff for: problems/0102.二叉树的层序遍历.md

@@ -246,6 +246,34 @@ var levelOrder = function(root) {
 
 ```
 
+Swift:
+```swift
+func levelOrder(_ root: TreeNode?) -> [[Int]] {
+    var res = [[Int]]()
+    guard let root = root else {
+        return res
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var sub = [Int]()
+        for _ in 0 ..< size {
+            let node = queue.removeFirst()
+            sub.append(node.val)
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        res.append(sub)
+    }
+    return res
+}
+```
+
 **此时我们就掌握了二叉树的层序遍历了，那么如下九道力扣上的题目，只需要修改模板的两三行代码（不能再多了），便可打倒！**
 
 
@@ -426,6 +454,31 @@ var levelOrderBottom = function(root) {
 };
 ```
 
+Swift:
+```swift
+func levelOrderBottom(_ root: TreeNode?) -> [[Int]] {
+    var res =  [[Int]]()
+    guard let root = root else {
+        return res
+    }
+    var queue:  [TreeNode] = [root]
+    while !queue.isEmpty {
+        var sub = [Int]()
+        for _ in 0 ..< queue.count {
+            let node = queue.removeFirst()
+            sub.append(node.val)
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        res.insert(sub, at: 0)
+    }
+    return res
+}
+```
 
 # 199.二叉树的右视图
 
@@ -604,6 +657,36 @@ var rightSideView = function(root) {
 };
 ```
 
+Swift:
+```swift
+func rightSideView(_ root: TreeNode?) -> [Int] {
+    var res = [Int]()
+    guard let root = root else {
+        return res
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        for i in 0 ..< size {
+            let node = queue.removeFirst()
+            if i == size - 1 {
+                // 保存 每层最后一个元素
+                res.append(node.val)
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return res
+}
+```
+
+
 # 637.二叉树的层平均值
 
 [力扣题目链接](https://leetcode-cn.com/problems/average-of-levels-in-binary-tree/)
@@ -785,6 +868,34 @@ var averageOfLevels = function(root) {
 };
 ```
 
+Swift:
+```swift
+func averageOfLevels(_ root: TreeNode?) -> [Double] {
+    var res = [Double]()
+    guard let root = root else {
+        return res
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var sum = 0
+        for _ in 0 ..< size {
+            let node = queue.removeFirst()
+            sum += node.val
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        res.append(Double(sum) / Double(size))
+    }
+    return res
+}
+```
+
 # 429.N叉树的层序遍历
 
 [力扣题目链接](https://leetcode-cn.com/problems/n-ary-tree-level-order-traversal/)
@@ -981,6 +1092,31 @@ var levelOrder = function(root) {
 };
 ```
 
+Swift:
+```swift
+func levelOrder(_ root: Node?) -> [[Int]] {
+    var res = [[Int]]()
+    guard let root = root else {
+        return res
+    }
+    var queue = [Node]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var sub = [Int]()
+        for _ in 0 ..< size {
+            let node = queue.removeFirst()
+            sub.append(node.val)
+            for childNode in node.children {
+                queue.append(childNode)
+            }
+        }
+        res.append(sub)
+    }
+    return res
+}
+```
+
 # 515.在每个树行中找最大值
 
 [力扣题目链接](https://leetcode-cn.com/problems/find-largest-value-in-each-tree-row/)
@@ -1136,6 +1272,36 @@ var largestValues = function(root) {
 };
 ```
 
+Swift:
+```swift
+func largestValues(_ root: TreeNode?) -> [Int] {
+    var res = [Int]()
+    guard let root = root else {
+        return res
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var max: Int = Int.min
+        for _ in 0 ..< size {
+            let node = queue.removeFirst()
+            if node.val > max {
+                max = node.val
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        res.append(max)
+    }
+    return res
+}
+```
+
 # 116.填充每个节点的下一个右侧节点指针
 
 [力扣题目链接](https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node/)
@@ -1338,6 +1504,37 @@ func connect(root *Node) *Node {
 }
 ```
 
+Swift:
+```swift
+func connect(_ root: Node?) -> Node? {
+    guard let root = root else {
+        return nil
+    }
+    var queue = [Node]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var preNode: Node?
+        for i in 0 ..< size {
+            let node = queue.removeFirst()
+            if i == 0 {
+                preNode = node
+            } else {
+                preNode?.next = node
+                preNode = node
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return root
+}
+```
+
 # 117.填充每个节点的下一个右侧节点指针II
 
 [力扣题目链接](https://leetcode-cn.com/problems/populating-next-right-pointers-in-each-node-ii/)
@@ -1532,6 +1729,38 @@ func connect(root *Node) *Node {
     return root
 }
 ```
+
+Swift：
+```swift
+func connect(_ root: Node?) -> Node? {
+    guard let root = root else {
+        return nil
+    }
+    var queue = [Node]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let size = queue.count
+        var preNode: Node?
+        for i in 0 ..< size {
+            let node = queue.removeFirst()
+            if i == 0 {
+                preNode = node
+            } else {
+                preNode?.next = node
+                preNode = node
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return root
+}
+```
+
 # 104.二叉树的最大深度
 
 [力扣题目链接](https://leetcode-cn.com/problems/maximum-depth-of-binary-tree/)
@@ -1704,6 +1933,31 @@ var maxDepth = function(root) {
 };
 ```
 
+Swift:
+```swift
+func maxDepth(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    var res: Int = 0
+    while !queue.isEmpty {
+        for _ in 0 ..< queue.count {
+            let node = queue.removeFirst()
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+        res += 1
+    }
+    return res
+}
+```
+
 # 111.二叉树的最小深度
 
 [力扣题目链接](https://leetcode-cn.com/problems/minimum-depth-of-binary-tree/)
@@ -1876,7 +2130,33 @@ var minDepth = function(root) {
 };
 ```
 
-
+Swift：
+```swift
+func minDepth(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    var res = 0
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        res += 1
+        for _ in 0 ..< queue.count {
+            let node = queue.removeFirst()
+            if node.left == nil && node.right == nil {
+                return res
+            }
+            if let left = node.left {
+                queue.append(left)
+            }
+            if let right = node.right {
+                queue.append(right)
+            }
+        }
+    }
+    return res
+}
+```
 
 
 # 总结

Diff for: problems/0226.翻转二叉树.md

@@ -609,5 +609,43 @@ struct TreeNode* invertTree(struct TreeNode* root){
 }
 ```
 
+### Swift：
+```swift
+// 前序遍历-递归
+func invertTree(_ root: TreeNode?) -> TreeNode? {
+    guard let root = root else {
+        return root
+    }
+    let tmp = root.left
+    root.left = root.right
+    root.right = tmp
+    let _ = invertTree(root.left)
+    let _ = invertTree(root.right)
+    return root
+}
+
+// 层序遍历-迭代
+func invertTree1(_ root: TreeNode?) -> TreeNode? {
+    guard let root = root else {
+        return nil
+    }
+    var queue = [TreeNode]()
+    queue.append(root)
+    while !queue.isEmpty {
+        let node = queue.removeFirst()
+        let tmp = node.left
+        node.left = node.right
+        node.right = tmp
+        if let left = node.left {
+            queue.append(left)
+        }
+        if let right = node.right {
+            queue.append(right)
+        }
+    }
+    return root
+}
+```
+
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 <div align="center"><img src=https://code-thinking.cdn.bcebos.com/pics/01二维码一.jpg width=500> </img></div>