Time: 1 ms (99.07%) | Memory: 42.1 MB (96.09%) - LeetSync

Author: ErAdnanHabib

257-binary-tree-paths/binary-tree-paths.java

@@ -17,21 +17,23 @@ class Solution {
  public List<String> binaryTreePaths(TreeNode root) {
 
  List<String> list = new ArrayList<>();
- dfs(root , "" , list);
+ StringBuilder sb = new StringBuilder();
+ dfs(root , sb , list);
  return list;
  }
- void dfs(TreeNode node , String path , List<String> list){
+ void dfs(TreeNode node , StringBuilder sb , List<String> list){
 
  if(node==null)return;
+ int len =sb.length();
 
- path += node.val;
+ sb.append(node.val);
 
  if(node.left==null && node.right==null){
- list.add(path);
- }else{
- path +="->";
- dfs(node.left , path , list);
- dfs(node.right , path , list);
+ list.add(sb.toString());
  }
+ sb.append("->");
+ dfs(node.left , sb , list);
+ dfs(node.right , sb , list);
+ sb.setLength(len);
  }
 }