LeetCode 数据结构入门 Day12 树 Java

LeetCode 数据结构入门 Day12 树 Java

226. 翻转二叉树

问题描述:

 代码:

class Solution {
    public TreeNode invertTree(TreeNode root) {
      if(root==null)
        return null;
        Queue queue = new linkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();
            TreeNode new1 = new TreeNode();
            new1 = node.left;
            node.left = node.right;
            node.right =new1;
            if(node.left!=null) 
                queue.offer(node.left);
            if(node.right!=null)
                queue.offer(node.right);

        }
        return root;
    }
}

思路:

层序遍历

112. 路径总和

问题描述:

代码:

class Solution {
    public boolean hasPathSum(TreeNode root, int targetSum) {
       if(root==null)
        return false;
        Queue tree = new linkedList<>();
        Queue val1 = new linkedList<>();
        tree.offer(root);
        val1.offer(root.val);
        while(!tree.isEmpty()){
            TreeNode a = tree.poll();
            int t = val1.poll();
            if(a.left==null&&a.right==null){
                if(t==targetSum)        
                    return true;
                continue;
            }
            if(a.left!=null){
                tree.offer(a.left);
                val1.offer(a.left.val+t);
            }
            if(a.right!=null){
                tree.offer(a.right);
                val1.offer(a.right.val+t);
            }
        }
        return false;
    }
}

思路: