【回溯】二叉树的所有路径

求解代码

publicList<String>binaryTreePaths(TreeNoderoot){List<String>ans=newArrayList<>();if(root==null){returnans;}StringBuildersb=newStringBuilder();backtrack(root,sb,ans);returnans;}privatevoidbacktrack(TreeNoderoot,StringBuildersb,List<String>ans){if(root==null){return;}// 记录当前拼接前的长度，用于回溯撤销intlen=sb.length();sb.append(root.val);// 到达叶子节点，添加完整路径if(root.left==null&&root.right==null){ans.add(sb.toString());}else{sb.append("->");backtrack(root.left,sb,ans);backtrack(root.right,sb,ans);}// 回溯撤销，恢复StringBuilder到拼接前的状态sb.setLength(len);}