LeetCode46|求根到叶子节点数字之和

 
public class SumNumbersTest {
    private static int sum = 0;

    public static void main(String[] args) {
        TreeNode t1 = new TreeNode(4);
        TreeNode t2 = new TreeNode(9);
        TreeNode t3 = new TreeNode(0);
        TreeNode t4 = new TreeNode(5);
        TreeNode t5 = new TreeNode(1);
        t1.left = t2;
        t1.right = t3;
        t2.left = t4;
        t2.right = t5;
        int sumValue = sumNumbers(t1);
        System.out.println("sumValue = " + sumValue);

    }

    public static int sumNumbers(TreeNode root) {
        if (root == null) {
            return sum;
        }
        computeSum(root, 0);
        return sum;
    }

    private static void computeSum(TreeNode root, int father) {
        if (root == null) {
            return;
        }
        int current = father * 10 + root.val;
        if (root.left == null && root.right == null) {
            sum += current;
            return;
        }
        computeSum(root.left, current);
        computeSum(root.right, current);
    }
}