257:二叉树的所有路径

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

@@ -26,40 +26,49 @@ import java.util.ArrayList;
 import java.util.List;
 
 //257:二叉树的所有路径
-public class BinaryTreePaths{
+public class BinaryTreePaths {
     public static void main(String[] args) {
         //测试代码
         Solution solution = new BinaryTreePaths().new Solution();
     }
     //力扣代码
     //leetcode submit region begin(Prohibit modification and deletion)
-/**
- * Definition for a binary tree node.
- * public class TreeNode {
- *     int val;
- *     TreeNode left;
- *     TreeNode right;
- *     TreeNode() {}
- *     TreeNode(int val) { this.val = val; }
- *     TreeNode(int val, TreeNode left, TreeNode right) {
- *         this.val = val;
- *         this.left = left;
- *         this.right = right;
- *     }
- * }
- */
-class Solution {
-    public List<String> binaryTreePaths(TreeNode root) {
-        if(root==null){
-            return null;
+
+    /**
+     * Definition for a binary tree node.
+     * public class TreeNode {
+     * int val;
+     * TreeNode left;
+     * TreeNode right;
+     * TreeNode() {}
+     * TreeNode(int val) { this.val = val; }
+     * TreeNode(int val, TreeNode left, TreeNode right) {
+     * this.val = val;
+     * this.left = left;
+     * this.right = right;
+     * }
+     * }
+     */
+    class Solution {
+        public List<String> binaryTreePaths(TreeNode root) {
+            List<String> paths = new ArrayList<String>();
+            dfs(root, "", paths);
+            return paths;
         }
-        List<String> list = new ArrayList<>();
-        if(root.left!=null){}
 
-
-        return list;
+        public void dfs(TreeNode root, String path, List<String> paths) {
+            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)
 
 }