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  1. import java.util.*;
  2.  
  3. public class Main {
  4.     static class Node {
  5.         Node left;
  6.         Node right;
  7.         int data;
  8.         Node(int data) {
  9.             this.data = data;
  10.         }
  11.     }
  12.  
  13.     static Node buildTree(int[] vals) {
  14.         if (vals.length == 0 || vals[0] == -1) return null;
  15.         Node root = new Node(vals[0]);
  16.         Queue<Node> q = new LinkedList<>();
  17.         q.offer(root);
  18.         int i = 1;
  19.         while (!q.isEmpty() && i < vals.length) {
  20.             Node curr = q.poll();
  21.             if (i < vals.length && vals[i] != -1) {
  22.                 curr.left = new Node(vals[i]);
  23.                 q.offer(curr.left);
  24.             }
  25.             i++;
  26.             if (i < vals.length && vals[i] != -1) {
  27.                 curr.right = new Node(vals[i]);
  28.                 q.offer(curr.right);
  29.             }
  30.             i++;
  31.         }
  32.         return root;
  33.     }
  34.  
  35.     static List<Integer> res = new ArrayList<>();
  36.  
  37.     static void seq(Node root) {
  38.         if (root == null) return;
  39.         seq(root.left);
  40.         res.add(root.data);
  41.         seq(root.right);
  42.     }
  43.  
  44.     public static void main(String[] args) {
  45.         Scanner sc = new Scanner(System.in);
  46.         int n = sc.nextInt();
  47.         int[] vals = new int[n];
  48.         for (int i = 0; i < n; i++) {
  49.             vals[i] = sc.nextInt();
  50.         }
  51.  
  52.         Node root = buildTree(vals);
  53.         seq(root);
  54.  
  55.         StringBuilder sb = new StringBuilder();
  56.         for (int i = 0; i < res.size(); i++) {
  57.             sb.append(res.get(i));
  58.             if (i != res.size() - 1) sb.append(" ");
  59.         }
  60.         System.out.println(sb.toString());
  61.     }
  62. }
Success #stdin #stdout 0.14s 50412KB
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1 2 3 4 5 -1 -1
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4 2 5 1 3
https://ideone.com/TWzVRM
language:
Java (HotSpot 12)
created:
3 days ago
visibility:
public

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