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257.java
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257.java
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__________________________________________________________________________________________________
sample 1 ms submission
/**
* 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> ans = new ArrayList<>();
dfs(root, new String(), ans);
return ans;
}
private void dfs(TreeNode root, String s, List<String> ans) {
if (root == null) {
return;
}
if (root.left == null && root.right == null) {
ans.add(s + root.val);
return;
}
dfs(root.left, s + root.val + "->", ans);
dfs(root.right, s + root.val + "->", ans);
}
}
__________________________________________________________________________________________________
sample 35900 kb submission
/**
* 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) {
return list;
}
String s = "";
helper(root, list, s);
return list;
}
public void helper(TreeNode root, List<String> list, String s) {
s += root.val;
if (root.left == null && root.right == null) {
list.add(s);
return;
}
if (root.left != null) {
helper(root.left, list, s = s + "->");
s = s.substring(0, s.length() - 2);
}
if (root.right != null) {
helper(root.right, list, s = s + "->");
s = s.substring(0, s.length() - 2);
}
}
}
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