1991. 트리 순회 (Java)

Node class 안의 left Node right Node 를 구현하여 이진트리를 구현해 내었고

출력위치를 조정하여 

전위, 중위, 후위 순회를 구현해 냈다.

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

class Node{
    char value;
    Node left;
    Node right;

    public Node(char value, Node left, Node right) {
        this.value = value;
        this.left = left;
        this.right = right;
    }
}
public class b1991 {

    static int N;
    static Node head = new Node('A',null,null);

    public static void insertNode(Node temp, char root, char left, char right) {

        if (temp.value == 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);
        }
    }
    public static void preOrder(Node node) {
        if(node ==null) return;
        System.out.print(node.value);
        preOrder(node.left);
        preOrder(node.right);
    }

    public static void inOrder(Node node) {
        if(node ==null) return;
        inOrder(node.left);
        System.out.print(node.value);
        inOrder(node.right);
    }

    public static void postOrder(Node node) {
        if(node ==null) return;
        postOrder(node.left);
        postOrder(node.right);
        System.out.print(node.value);
    }

    public static void main(String[] args) throws IOException {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        N = Integer.parseInt(br.readLine());

        for(int i = 0 ; i < N ; i++){
            StringTokenizer st = new StringTokenizer(br.readLine());
            char value = st.nextToken().charAt(0);
            char left = st.nextToken().charAt(0);
            char right = st.nextToken().charAt(0);
            insertNode(head,value,left,right);
        }
        preOrder(head);
        System.out.println();
        inOrder(head);
        System.out.println();
        postOrder(head);
        System.out.println();
    }
}