Leetcode 1530. Number of Good Leaf Nodes Pairs Attempt#1

Solution.java

/**
1530. Number of Good Leaf Nodes Pairs
Attempt#1
https://leetcode.com/problems/number-of-good-leaf-nodes-pairs/
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public int countPairs(TreeNode root, int distance) {
        int[] result = new int[1];
        dfs(root, result, distance);
        return result[0];
    }

    private int[] dfs(TreeNode node, int[] result, int d) {
        if (node.left == null && node.right == null) {
            int[] dist = new int[d+1];
            dist[0] = 1;
            return dist;
        }

        int[] dist = new int[d+1];
        int[] distLeft = null;
        if (node.left != null) {
            distLeft =  dfs(node.left, result, d);
            for (int i = d; i >= 1; i--) {
                distLeft[i] = distLeft[i-1];
            }
            distLeft[0] = 0;

            System.out.print("distLeft: ");
            for (int i = 0; i < distLeft.length; i++) {
                System.out.print(distLeft[i] + ", ");
            }
            System.out.print("\n");
            
        }
        int[] distRight = null;
        if (node.right != null) {
            distRight =  dfs(node.right, result, d);
            for (int i = d; i >= 1; i--) {
                distRight[i] = distRight[i-1];
            }
            distRight[0] = 0;

            System.out.print("distRigth: ");
            for (int i = 0; i < distRight.length; i++) {
                System.out.print(distRight[i] + ", ");
            }
            System.out.print("\n");
        }
        for (int i = 0; i <= d; i++) {
            dist[i] = (distLeft == null ? 0 : distLeft[i])
                + (distRight == null ? 0 : distRight[i]);
        }
        if (distLeft != null && distRight != null) {
            for (int i = 1; i <= d; i++) {
                for (int l = 1; l <= i-1; l++) {
                    if (distLeft[l] > 0 && distRight[i-l] > 0) {
                        int delta = Math.min(distLeft[l], distRight[i-l]);
                        result[0] += delta;
                        distLeft[l] -= delta;
                        distRight[i-l] -= delta;
                    }
                }
            }
        }
        return dist;
    }
}