java非递归写法

bfs,对分层打印二叉树进行改进。遍历完一层就加1

//  非递归类似分层打印。bfs
class Solution {
    static int ans = 0;
    public int treeDepth(TreeNode root) {
        bfs(root);
        return ans;
    }
    public void bfs(TreeNode root) {
        if(root == null) return;
        Queue<TreeNode> q = new LinkedList<>();
        q.offer(root);
        while(!q.isEmpty()) {
            int size = q.size();
            // 这是一层的
            for(int i = 0; i < size; i++) {
                TreeNode tmp = q.poll();
                if(tmp.left != null) q.offer(tmp.left);
                if(tmp.right != null) q.offer(tmp.right);
            }
            ans++;
        }

    }
}