[백준 1991] 트리순회

https://www.acmicpc.net/problem/1991

1991번: 트리 순회

 

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;

public class Main {

	static Node rootNode = new Node('A', null, null);
	
	static class Node{
		char name;
		Node left;
		Node right;
		
		public Node(char name, Node left, Node right) {
			this.name = name;
			this.left = left;
			this.right = right;
		}
	}

	static void addNode(Node node, char head, char left, char right) {
		if(node.name==head) {
			node.left = (left=='.' ? null : new Node(left, null, null));
			node.right = (right=='.' ? null : new Node(right, null, null));
		}
		else {
			if(node.left!=null) addNode(node.left, head, left, right);
			if(node.right!=null) addNode(node.right, head, left, right);
		}
	}
	
	
	static void preOrder(Node node) {
		if(node ==null) return;
		System.out.print(node.name);
		preOrder(node.left);
		preOrder(node.right);
	}
	static void inOrder(Node node) {
		if(node ==null) return;
		inOrder(node.left);
		System.out.print(node.name);
		inOrder(node.right);
	}
	static void postOrder(Node node) {
		if(node ==null) return;
		postOrder(node.left);
		postOrder(node.right);
		System.out.print(node.name);
	}

	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		
		int n = Integer.parseInt(br.readLine());
		
		for(int i=0; i<n; i++) {
			StringTokenizer stk = new StringTokenizer(br.readLine());
			
			char head = stk.nextToken().charAt(0);
			char left = stk.nextToken().charAt(0);
			char right = stk.nextToken().charAt(0);
			
			addNode(rootNode, head, left, right);
		}
		
		preOrder(rootNode);
		System.out.println();
		inOrder(rootNode);
		System.out.println();
		postOrder(rootNode);
	}
}