lint0175. 0480.

• 反转一棵二叉树

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */
public class Solution {
    /**
     * @param root: a TreeNode, the root of the binary tree
     * @return: nothing
     */
    public void invertBinaryTree(TreeNode root) {
        if(root==null)
            return;
        TreeNode tmp = root.left;
        root.left = root.right;
        root.right = tmp;
        invertBinaryTree(root.left);
        invertBinaryTree(root.right);
    }
}

• 480. Binary Tree Paths

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: the root of the binary tree
     * @return: all root-to-leaf paths
     */
    public List<String> binaryTreePaths(TreeNode root) {
        List<String> ret = new ArrayList<>();
        if(root==null)
            return ret;
        List<String> lret = binaryTreePaths(root.left);
        List<String> rret = binaryTreePaths(root.right);
        for(String path : lret){
            ret.add(root.val+"->"+path);
        }
        for(String path : rret){
            ret.add(root.val+"->"+path);
        }
        if(ret.size()==0)
            ret.add(""+root.val);
        return ret;
    }
}