leetcode-algorithms/src/SumRootToLeafNumbers.java at master · anishLearnsToCode/leetcode-algorithms · GitHub

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// https://leetcode.com/problems/sum-root-to-leaf-numbers

// T: O(n)

// S: O(log(n))

public class SumRootToLeafNumbers {

public int sumNumbers(TreeNode root) {

return sumNumbers(root, 0);

}

private int sumNumbers(TreeNode root, int currentSum) {

if (root == null) return 0;

if (isLeafNode(root)) return 10 * currentSum + root.val;

return sumNumbers(root.left, 10 * currentSum + root.val)

+ sumNumbers(root.right, 10 * currentSum + root.val);

}

private boolean isLeafNode(TreeNode root) {

return root.left == null && root.right == null;

}

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