GoodNodesInBinaryTree.java

package LeetcodePractice;

public class GoodNodesInBinaryTree {
    public static class TreeNode {
        int val;
        TreeNode left;
        TreeNode right;
        TreeNode(int val) { this.val = val; }
        TreeNode(int val, TreeNode left, TreeNode right) {
            this.val = val;
            this.left = left;
            this.right = right;
        }
    }

    public int goodNodes(TreeNode root) {
        return dfs(root, Integer.MIN_VALUE);
    }

    
    private int dfs(TreeNode node, int maxSoFar) {
        if (node == null) return 0;

        int count = 0;
        if (node.val >= maxSoFar) {
            count = 1; 
        }

        maxSoFar = Math.max(maxSoFar, node.val);

        count += dfs(node.left, maxSoFar);
        count += dfs(node.right, maxSoFar);

        return count;
    }

  
    public static TreeNode buildExampleTree1() {
        return new TreeNode(3,
            new TreeNode(1, new TreeNode(3), null),
            new TreeNode(4, new TreeNode(1), new TreeNode(5))
        );
    }

    public static void main(String[] args) {
        GoodNodesInBinaryTree solution = new GoodNodesInBinaryTree();
        TreeNode root = buildExampleTree1();
        int result = solution.goodNodes(root);
        System.out.println("Number of good nodes: " + result);  
    }
}