程序员代码面试指南刷题--第三章.直观的打印树

问题：设计一种打印方法直观的打印树的结构

输入描述:

第一行输入两个整数 n 和 root，n 表示二叉树的总节点个数，root 表示二叉树的根节点。

以下 n 行每行三个整数 fa，lch，rch，表示 fa 的左儿子为 lch，右儿子为 rch。(如果 lch 为 0 则表示 fa 没有左儿子，rch同理)

输入

8 1
1 2 3
2 4 5
4 0 0
5 0 0
3 6 7
6 0 0
7 8 0
8 0 0

解法一：递归打印

import java.io.*;
import java.util.*;
public class Main{
    public static void main(String[] args)throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        br.readLine();
        TreeNode root = createTree(br);
        printTree(root,0,"H",17);
    }
    public static void printTree(TreeNode root,int height,String s,int len) {
    	if(root==null) return;
    	printTree(root.right,height+1,"v",len);
    	String val = s+root.val+s;
    	int length = val.length();
    	int left = (len-length)/2;
    	int right = len-left-length;
    	String realVal = getSpace(left)+val+getSpace(right);
    	System.out.println(getSpace(height*len)+realVal);
    	printTree(root.left,height+1,"^",len);
    }
    public static String getSpace(int len) {
    	StringBuilder sb = new StringBuilder();
    	for(int i=0;i<len;i++) {
    		sb.append(" ");
    	}
    	return sb.toString();
    }
    //递归建树
    public static TreeNode createTree(BufferedReader br){
        try{
            String[] ss = br.readLine().trim().split(" ");
            int data = Integer.parseInt(ss[0]);
            int left = Integer.parseInt(ss[1]);
            int right = Integer.parseInt(ss[2]);
            TreeNode root = new TreeNode(data);
            if(left!=0){
                root.left = createTree(br);
            }
            if(right!=0){
                root.right = createTree(br);
            }
            return root;
        }catch(Exception e){
            return null;
        }
    }
}
class TreeNode{
    int val;
    TreeNode left;
    TreeNode right;
    public TreeNode(int val){
        this.val = val;
    }
}