二叉树第K层结点个数

二叉树第K层结点个数

public class ErChaShuKCengJieDianGeShu {
	public static void main(String[] args) {
		TreeNode root = new TreeNode(1);
		root.left = new TreeNode(2);
		root.right = new TreeNode(3);
		root.left.left = new TreeNode(4);
		root.left.right = new TreeNode(5);
		root.right.left = new TreeNode(6);
		root.right.right = new TreeNode(7);		
		ErChaShuKCengJieDianGeShuSolution solution = new ErChaShuKCengJieDianGeShuSolution();
		System.out.println(solution.solution(root, 1));
	}
}

class ErChaShuKCengJieDianGeShuSolution {
	public int solution(TreeNode root,int k) {
		if(root == null) return 0;
		k--;
		if(k==0) return 1;
		int left = solution(root.left, k);
		int right = solution(root.right, k);
		return left+right;
	}
}