【leetcode】222（Medium）Count Complete Tree Nodes

解题思路

可以用morris遍历，或者递归

提交代码：morris

class Solution {
    public int countNodes(TreeNode root) {
        int res=0;
        
        TreeNode p1=root,p2=root;
        while(p1!=null) {
        	if(p1.left!=null) {
        		p2=p1.left;
        		while(p2.right!=null&&p2.right!=p1)
        			p2=p2.right;
        		
        		if(p2.right==null) {
        			p2.right=p1;
        			p1=p1.left;
        		}
        		else {
        			res++;
        			p2.right=null;
        			p1=p1.right;
        		}
        	}else {
        		res++;
        		p1=p1.right;
        	}
        }
        return res;
    }
}

运行结果

提交代码：递归

class Solution {
	public int countNodes(TreeNode root) {
		if(root==null)	return 0;
		return countNodes(root.left)+countNodes(root.right)+1;
	}
}

运行结果