剑指 从上到下打印二叉树

剑指 Offer 32 - I. 从上到下打印二叉树

java

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public int[] levelOrder(TreeNode root) { if(root == null) return new int[0]; Queue<TreeNode> queue = new LinkedList<>(); ArrayList<Integer> res = new ArrayList<>(); return forEacher( root,queue ,res); } int[] forEacher(TreeNode root,Queue<TreeNode> queue ,ArrayList<Integer> res){ queue.add(root); while(!queue.isEmpty()){ TreeNode tmp = queue.poll(); res.add(tmp.val); if(tmp.left!=null) queue.add(tmp.left); if(tmp.right!=null) queue.add(tmp.right); } int[] d = new int[res.size()]; for(int i = 0;i<res.size();i++){ d[i] = res.get(i); } return d; } }

剑指 Offer 32 - II. 从上到下打印二叉树 II

java

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public List<List<Integer>> levelOrder(TreeNode root) { Queue<TreeNode> queue = new LinkedList<>(); List<List<Integer>> res = new ArrayList<>(); if(root != null) queue.add(root); while(!queue.isEmpty()){ List<Integer> node = new ArrayList<>(); for(int i=queue.size();i>0;i--){ TreeNode tmp = queue.poll(); node.add(tmp.val); if(tmp.left!=null) queue.add(tmp.left); if(tmp.right!=null) queue.add(tmp.right); } res.add(node); } return res; } }

剑指 Offer 32 - III. 从上到下打印二叉树 III

java

/** * Definition for a binary tree node. * public class TreeNode { * int val; * TreeNode left; * TreeNode right; * TreeNode(int x) { val = x; } * } */ class Solution { public List<List<Integer>> levelOrder(TreeNode root) { Queue<TreeNode> queue = new LinkedList<>(); List<List<Integer>> res = new ArrayList<>(); if(root != null) queue.add(root); while(!queue.isEmpty()){ List<Integer> node = new ArrayList<>(); for(int i=queue.size();i>0;i--){ TreeNode tmp = queue.poll(); node.add(tmp.val); if(tmp.left!=null) queue.add(tmp.left); if(tmp.right!=null) queue.add(tmp.right); } res.add(node); } return res; } }