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This approach uses Depth-First Search (DFS) to explore all paths from the root to the leaf nodes. Starting from the root, we recursively visit each node, accumulating the current path. When a leaf node is reached, we add the accumulated path to a list of paths. This can be implemented recursively and is optimal given the constraints.
Time Complexity: O(n), where n is the number of nodes in the tree, as we visit each node once.
Space Complexity: O(n), for the space used to store the recursion stack and the result paths.
1var binaryTreePaths = function(root) {
2 const paths = [];
3 const dfs = (node, path) => {
4 if (node) {
5 path += node.val;
6 if (!node.left && !node.right) {
7 paths.push(path);
8 } else {
9 path += '->';
10 dfs(node.left, path);
11 dfs(node.right, path);
12 }
13 }
14 };
15 dfs(root, '');
16 return paths;
17};This JavaScript solution leverages a DFS strategy within an inner function, recursively navigating the tree and building paths, which are stored when a leaf node is reached.
This approach utilizes an iterative Depth-First Search (DFS) with a stack. By storing the nodes and their paths on the stack, we can simulate the recursive DFS stack. This allows for constructing the paths through iterative backtracking.
Time Complexity: O(n), traversing each node once.
Space Complexity: O(n), as we maintain a stack proportional to the tree height.
1using System.Collections.Generic;
public class TreeNode {
public int val;
public TreeNode left;
public TreeNode right;
public TreeNode(int x) { val = x; }
}
public class Solution {
public IList<string> BinaryTreePaths(TreeNode root) {
List<string> paths = new List<string>();
if (root == null) return paths;
Stack<(TreeNode, string)> stack = new Stack<(TreeNode, string)>();
stack.Push((root, root.val.ToString()));
while (stack.Count > 0) {
var (node, path) = stack.Pop();
if (node.left == null && node.right == null) {
paths.Add(path);
}
if (node.right != null) {
stack.Push((node.right, path + "->" + node.right.val));
}
if (node.left != null) {
stack.Push((node.left, path + "->" + node.left.val));
}
}
return paths;
}
}This C# solution uses a stack to iteratively explore the tree, simulating recursive behavior through stack operations. The process accumulates paths, finalizing them once a leaf node is identified.