solve 257.二叉树的所有路径

Author: andavid

zh/257.二叉树的所有路径.java

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+/*
+ * @lc app=leetcode.cn id=257 lang=java
+ *
+ * [257] 二叉树的所有路径
+ *
+ * https://leetcode-cn.com/problems/binary-tree-paths/description/
+ *
+ * algorithms
+ * Easy (63.85%)
+ * Likes:    262
+ * Dislikes: 0
+ * Total Accepted:    37.4K
+ * Total Submissions: 58.6K
+ * Testcase Example:  '[1,2,3,null,5]'
+ *
+ * 给定一个二叉树，返回所有从根节点到叶子节点的路径。
+ *
+ * 说明: 叶子节点是指没有子节点的节点。
+ *
+ * 示例:
+ *
+ * 输入:
+ *
+ * ⁠  1
+ * ⁠/   \
+ * 2     3
+ * ⁠\
+ * ⁠ 5
+ *
+ * 输出: ["1->2->5", "1->3"]
+ *
+ * 解释: 所有根节点到叶子节点的路径为: 1->2->5, 1->3
+ *
+ */
+
+// @lc code=start
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     int val;
+ *     TreeNode left;
+ *     TreeNode right;
+ *     TreeNode(int x) { val = x; }
+ * }
+ */
+class Solution {
+  public List<String> binaryTreePaths(TreeNode root) {
+    List<String> list = new ArrayList<>();
+    if (root != null) {
+      dfs(list, "", root);
+    }
+    return list;
+  }
+
+  public void dfs(List<String> list, String path, TreeNode root) {
+    if (root.left == null && root.right == null) {
+      list.add(path + root.val);
+    } else {
+      if (root.left != null) {
+        dfs(list, path + root.val + "->", root.left);
+      }
+      if (root.right != null) {
+        dfs(list, path + root.val + "->", root.right);
+      }
+    }
+  }
+}
+// @lc code=end
+