백준 1991

문제

---

Code

package test;

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

public class P1991 {
	
	static class Node {
		char name;
		Node left;
		Node right;
		
		Node(char name, Node left, Node right) {
			this.name = name;
			this.left = left;
			this.right = right;
		}
	}

	static Node head = new Node('A', null, null);
	
	public static void main(String[] args) throws IOException {
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		StringTokenizer st;
		
		int N = Integer.parseInt(br.readLine());
		for(int i = 0; i < N; i++) {
			st = new StringTokenizer(br.readLine(), " ");
			char root = st.nextToken().charAt(0);
			char left = st.nextToken().charAt(0);
			char right = st.nextToken().charAt(0);
			insertNode(head, root, left, right);
		}
		preOrder(head);
		System.out.println();
		inOrder(head);
		System.out.println();
		postOrder(head);
		
	}
	private static void insertNode(Node temp, char root, char left, char right) {
		if(temp.name == root) {
			temp.left = (left == '.' ? null : new Node(left, null, null));
			temp.right = (right == '.' ? null : new Node(right, null, null));
		} else {
			if(temp.left != null) {
				insertNode(temp.left, root, left, right);
			} 
			if(temp.right != null) {
				insertNode(temp.right, root, left, right);
			}
		}
	}
	
	private static void preOrder(Node node) {
		if(node == null) {
			return;
		}
		System.out.print(node.name);
		preOrder(node.left);
		preOrder(node.right);
	}
	
	private static void inOrder(Node node) {
		if(node == null) {
			return;
		}
		inOrder(node.left);
		System.out.print(node.name);
		inOrder(node.right);
	}
	
	private static void postOrder(Node node) {
		if(node == null) {
			return;
		}
		postOrder(node.left);
		postOrder(node.right);
		System.out.print(node.name);
	}

}

---

참고 : https://velog.io/@gandi0330/Java-%EB%B0%B1%EC%A4%80-%ED%8A%B8%EB%A6%AC-%EC%88%9C%ED%9A%8C-1991%EB%B2%88