257:二叉树的所有路径

src/main/java/leetcode/editor/cn/BinaryTreePaths.java

@@ -33,6 +33,7 @@ public class BinaryTreePaths{
     }
     //力扣代码
     //leetcode submit region begin(Prohibit modification and deletion)
+
     /**
      * Definition for a binary tree node.
      * public class TreeNode {
@@ -50,14 +51,22 @@ public class BinaryTreePaths{
      */
     class Solution {
         public List<String> binaryTreePaths(TreeNode root) {
-        if(root==null){
+            List<String> paths = new ArrayList<String>();
-            return null;
+            dfs(root, "", paths);
+            return paths;
         }
-        List<String> list = new ArrayList<>();
-        if(root.left!=null){}
 
-
+        public void dfs(TreeNode root, String path, List<String> paths) {
-        return list;
+            if (root != null) {
+                path += root.val;
+                if (root.left == null && root.right == null) {
+                    paths.add(path);
+                } else {
+                    path += "->";
+                    dfs(root.left, path, paths);
+                    dfs(root.right, path, paths);
+                }
+            }
         }
     }
 //leetcode submit region end(Prohibit modification and deletion)