백준 1991 트리 순회(Java)

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

1991번: 트리 순회

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Java 코드

 

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import java.util.Scanner;

public class Main {

  static int n;
  static int[][] arr;
  static StringBuilder sb = new StringBuilder();

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    n = sc.nextInt();
    arr = new int[n][2];
   
    for(int i = 0; i < n; i++) {
      char c = sc.next().charAt(0);
      char l = sc.next().charAt(0);
      char r = sc.next().charAt(0);
      
      if(l == '.') arr[c - 'A'][0] = -1;
      else arr[c -'A'][0] = l - 'A';

      if(r == '.') arr[c - 'A'][1] = -1;
      else arr[c -'A'][1] = r - 'A';
    }

    pre(0);
    sb.append("\n");
    inor(0);
    sb.append("\n");
    post(0);
    sb.append("\n");
   
    System.out.println(sb);
  }

  public static void pre(int num) {
    if(num == -1) return;
    sb.append((char)(num + 'A'));
    pre(arr[num][0]);
    pre(arr[num][1]);
  }

  public static void inor(int num) {
    if(num == -1) return;
    inor(arr[num][0]);
    sb.append((char)(num + 'A'));
    inor(arr[num][1]);
  }

  public static void post(int num) {
    if(num == -1) return;
    post(arr[num][0]);
    post(arr[num][1]);
    sb.append((char)(num + 'A'));
  }

}