Binary Tree Paths Easy 0 attempts
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Binary Tree Paths

Easy TreeBinary TreeDFS LeetCode

You're given the root of a binary tree. Return every path that starts at the root and ends at a leaf, formatted as a string with -> joining the node values, in any order.

Input Format
Implement binaryTreePaths(root). Inputs below show JavaScript function arguments; there is no stdin parsing. Trees use level-order arrays with null for missing children. The editor passes nodes with val, left, and right properties; [] becomes null.
Output Format
Return the result described in the statement. The order of the outer result array does not matter.

Sample Input and Output

Example 1 · Run Sample

Input
root = [1,2,3,null,5]
Output
["1->2->5","1->3"]

Example 2

Input
root = [1]
Output
["1"]
Constraints
  • 1 <= number of nodes <= 100
  • -100 <= Node.val <= 100
Test Cases (2)
Case 1
Args: [[1,2,3,null,5]] Expected: ["1->2->5","1->3"]
Case 2
Args: [[1]] Expected: ["1"]
Topics
TreeBinary TreeDFS

DFS with Path Tracking

javascript
function binaryTreePaths(root) {
  const result = [];
  function dfs(node, path) {
    if (!node) return;
    path += node.val;
    if (!node.left && !node.right) { result.push(path); return; }
    dfs(node.left, path + '->');
    dfs(node.right, path + '->');
  }
  dfs(root, '');
  return result;
}

Time: O(n × h) as a loose upper bound for path strings, where h is tree height | Space: O(h²) auxiliary string storage in the worst case, excluding output

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JavaScript