添加 513. 找树左下角的值 Swift 版本

problems/0513.找树左下角的值.md

@@ -433,6 +433,74 @@ var findBottomLeftValue = function(root) {
 };
 ```
 
+## Swift 
+
+递归版本：
+
+```swift
+var maxLen = -1
+var maxLeftValue = 0
+func findBottomLeftValue_2(_ root: TreeNode?) -> Int {
+    traversal(root, 0)
+    return maxLeftValue
+}
+
+func traversal(_ root: TreeNode?, _ deep: Int) {
+    guard let root = root else {
+        return
+    }
+
+    if root.left == nil && root.right == nil {
+        if deep > maxLen {
+            maxLen = deep
+            maxLeftValue = root.val
+        }
+        return
+    }
+    
+    if root.left != nil {
+        traversal(root.left, deep + 1)
+    }
+    
+    if root.right != nil {
+        traversal(root.right, deep + 1)
+    }
+    return
+}
+```
+层序遍历：
+
+```swift
+func findBottomLeftValue(_ root: TreeNode?) -> Int {
+    guard let root = root else {
+        return 0
+    }
+    
+    var queue = [root]
+    var result = 0
+    
+    while !queue.isEmpty {
+        let size = queue.count
+        for i in 0..<size {
+            let firstNode = queue.removeFirst()
+          
+            if i == 0 {
+                result = firstNode.val
+            }
+            
+            if let leftNode = firstNode.left {
+                queue.append(leftNode)
+            }
+            
+            if let rightNode = firstNode.right {
+                queue.append(rightNode)
+            }
+        }
+    }
+    return result
+}
+```
+
 
 
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