257. Binary Tree Paths

Author: TBXark

257. Binary Tree Paths.md

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+# 257. Binary Tree Paths
+
+### 2017-03-21
+
+Given a binary tree, return all root-to-leaf paths.
+
+For example, given the following binary tree:
+
+```
+   1
+ /   \
+2     3
+ \
+  5
+
+```
+
+All root-to-leaf paths are:
+
+```
+["1->2->5", "1->3"]
+```
+
+
+
+# Solution
+
+```swift
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+class Solution {
+    func binaryTreePaths(_ root: TreeNode?) -> [String] {
+        guard let n = root else { return [] }
+        var path = [String]()
+        if n.left == nil && n.right == nil { return ["\(n.val)"]}
+        for p in binaryTreePaths(n.left) {
+            path.append("\(n.val)->\(p)")
+        }
+        for p in binaryTreePaths(n.right) {
+            path.append("\(n.val)->\(p)")
+        }
+        return path
+    }
+}
+```
+