kingsubin

import java.io.*;
import java.util.StringTokenizer;
 
public class boj_1991 {
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static int n;
    static Node[] a;
 
    public static void main(String[] args) throws IOException {
        n = Integer.parseInt(br.readLine());
        a = new Node[n];
        for (int i = 0; i < n; i++) {
            st = new StringTokenizer(br.readLine());
            int x = st.nextToken().charAt(0) - 'A';
            char y = st.nextToken().charAt(0);
            char z = st.nextToken().charAt(0);
 
            int left = -1;
            int right = -1;
 
            if (y != '.') {
                left = y - 'A';
            }
            if (z != '.') {
                right = z - 'A';
            }
            a[x] = new Node(left, right);
        }
 
        preorder(0);
        System.out.println();
        inorder(0);
        System.out.println();
        postorder(0);
        System.out.println();
    }
 
    static void preorder(int x) {
        if (x == -1) return;
        System.out.print((char)(x + 'A'));
        preorder(a[x].left);
        preorder(a[x].right);
    }
    static void inorder(int x) {
        if (x == -1) return;
        inorder(a[x].left);
        System.out.print((char)(x + 'A'));
        inorder(a[x].right);
    }
    static void postorder(int x) {
        if (x == -1) return;
        postorder(a[x].left);
        postorder(a[x].right);
        System.out.print((char)(x + 'A'));
    }
}
 
class Node {
    int left;
    int right;
 
    public Node(int left, int right) {
        this.left = left;
        this.right = right;
    }
}

 

- 트리

 

- 전위순회, 중위순회, 후위순회를 구현

- 그냥 이론상으로만 아는걸 코드로 구현해보려고 하니깐 어렵다.

 

 

 

 

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www.acmicpc.net/problem/1991