Given a binary tree, return all root-to-leaf paths.
For example
Given the following binary tree:
All root-to-leaf paths are: ["1->2->5", "1->3"]
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| public class Solution {
public List<String> binaryTreePaths(TreeNode root) {
List<String> result = new ArrayList<>();
if (root == null) {
return result;
}
helper(result, new ArrayList<>(), root);
return result;
}
private void helper(List<String> result, List<Integer> crt, TreeNode root) {
if (root == null) {
return;
} else {
crt.add(root.val);
}
if (root.right == null && root.left == null) {
result.add(getString(crt));
return;
}
if (root.left != null) {
helper(result, new ArrayList<>(crt), root.left);
}
if (root.right != null) {
helper(result, new ArrayList<>(crt), root.right);
}
}
private String getString(List<Integer> crt) {
if (crt == null || crt.isEmpty()) {
return null;
}
StringBuilder sb = new StringBuilder();
sb.append(crt.get(0));
for (int i = 1; i < crt.size(); i++) {
sb.append("->").append(crt.get(i));
}
return sb.toString();
}
}
|