【java 面试100】16输入一颗二元树，从上往下按层打印树的每个结点

2024年6月9日 134次阅读

题目（微软）：
输入一颗二元树，从上往下按层打印树的每个结点，同一层中按照从左往右的顺序打印。  
例如输入

   8
  / /
 6 10
/ / / /
5 7 9 11

输出8 6 10 5 7 9 11。

使用队列，二叉树的广度优先遍历

public class PrintByLevel {
	public void printByLevel(BSTreeNode root){
		LinkedList<BSTreeNode> q=new LinkedList<BSTreeNode>();
		q.addFirst(root);
		while(!q.isEmpty()){
			BSTreeNode n=q.removeLast();
			System.out.print(n.value+" ");
			if(n.lefTreeNode!=null) q.addFirst(n.lefTreeNode);
			if(n.rightTreeNode!=null)q.addFirst(n.rightTreeNode);
			
		}
	}
	public static void main(String[] args) {
		BSTreeNode root=new BSTreeNode(8);
		BSTreeNode p6=new BSTreeNode(6);
		BSTreeNode p10=new BSTreeNode(10);
		BSTreeNode p5=new BSTreeNode(5);
		BSTreeNode p7=new BSTreeNode(7);
		BSTreeNode p9=new BSTreeNode(9);
		BSTreeNode p11=new BSTreeNode(11);
		root.lefTreeNode=p6;
		root.rightTreeNode=p10;
		p6.lefTreeNode=p5;
		p6.rightTreeNode=p7;
		p10.lefTreeNode=p9;
		p10.rightTreeNode=p11;
		PrintByLevel pByLevel=new PrintByLevel();
		pByLevel.printByLevel(root);
	}
}

class BSTreeNode{
	int value;
	BSTreeNode lefTreeNode;
	BSTreeNode rightTreeNode;
	public BSTreeNode(){}
	public BSTreeNode(int data){
		this.value=data;
	}
}

结果：8 6 10 5 7 9 11 

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