0257-binary-tree-paths

257. Binary Tree Paths

Problem Description

Given a binary tree, return all root-to-leaf paths.

Detail instruction can be found here.

Example 1:

Input:

   1
 /   \
2     3
 \
  5

Output: ["1->2->5", "1->3"]

Explanation: All root-to-leaf paths are: 1->2->5, 1->3

Solution

Approach 1: Recursive

public List<String> binaryTreePaths(TreeNode root) {
    List<String> paths = new ArrayList<>();
    dfs(root, "", paths);
    return paths;
}

private void dfs(TreeNode root, String path, List<String> paths) {
    if (root == null)   return;
    if (root.left == null && root.right == null) {
        path += root.val;
        paths.add(path);
    }
    path += (root.val + "->");
    dfs(root.left, path, paths);
    dfs(root.right, path, paths);
}

Approach 2: Iterative

// TODO

Definition for a Node

public class TreeNode {
    int val;
    TreeNode left;
    TreeNode right;
    TreeNode(int x) { val = x; }
}

Test

Compile with javac Solution.java and run with java Solution.

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