public class Main104 {

public static void main(String[] args){

Main104 main = new Main104();

main.test();

}

public void test(){

TreeNode root = new TreeNode(3);

root.left = new TreeNode(9);

root.right = new TreeNode(20);

root.right.left = new TreeNode(15);

root.right.right = new TreeNode(7);

System.out.println(maxDepth(root));

}

public int maxDepth(TreeNode root) {

int leftDep,rightDep,max;

if (root!=null){

leftDep = maxDepth(root.left);

rightDep = maxDepth(root.right);

max = leftDep>rightDep?leftDep:rightDep;

return max+1;

}

return 0;

}

private class TreeNode{

int val;

TreeNode left;

TreeNode right;

TreeNode(int x){

val = x;

}

}

}