<Algorithm> 43. 1991번 트리 순회

1. 1991번 트리 순회

• 기본 이진트리 알고리즘, preorder ( Root -> L -> R ) inorder (  L -> Root -> R )  postorder ( L -> R -> Root ) 

• 배열의 인덱스를 이용해서 트리를 생성하였다.

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;
 
public class Main {
    public static void main(String[] args) throws NumberFormatException, IOException {
        BufferedReader br =new BufferedReader(new InputStreamReader(System.in));
        StringTokenizer st = new StringTokenizer(br.readLine());
        int N = Integer.parseInt(st.nextToken());
        
        char temp[][] = new char[N][3];
        
        for(int i = 0; i < N; i ++) {
            st = new StringTokenizer(br.readLine());
            for(int j = 0; j < 3; j++) {
                temp[i][j] = st.nextToken().charAt(0);
            }
        }
        Tree tree[] = new Tree[100];
        
        
        for(int i = 0; i < N; i ++) {
            tree[temp[i][0]-'0'] = new Tree(temp[i][0],null,null);
        }
        
        
        for(int i = 0; i < N; i ++) {
            tree[temp[i][0]-'0'].left = ( temp[i][1] == '.') ? null : tree[temp[i][1]-'0'];
            tree[temp[i][0]-'0'].right = ( temp[i][2] == '.') ? null : tree[temp[i][2]-'0'];            
        }
        Tree root = tree[temp[0][0]-'0'];
        pre(root);
        System.out.println();
        in(root);
        System.out.println();
        post(root);
        
    }
    private static void pre(Tree root) {
    
        if(root != null) {    
            System.out.print(root.name);
            pre(root.left);
            pre(root.right);
        }
        
    }
    private static void in(Tree root) {
        if(root != null) {    
            in(root.left);
            System.out.print(root.name);
            in(root.right);
        }
    }
    private static void post(Tree root) {
        if(root != null) {
            post(root.left);
            post(root.right);
            System.out.print(root.name);
        }
    }
    
}
class Tree{
    char name;
    Tree left;
    Tree right;
    
    public Tree() {
        super();
    }
    public Tree(char name,Tree left, Tree right) {
        super();
        this.name = name;
        this.left = left;
        this.right = right;
    }
    
}