026 返回二叉树的所有叶子

1.题目

　　返回所有的叶子节点

2.程序

import java.util.List;
import java.util.Queue;
import java.util.LinkedList;

public class Leaf {
    //定义树节点
    public static class TreeNode{
        TreeNode left=null;
        TreeNode right=null;
        int value;
        TreeNode(int value){
            this.value=value;
        }
        @Override
        public String toString() {
            return "<TreeNode value:"+ this.value+">";
        }
    }
    //遍历叶子节点
    public List<TreeNode> getLeaf(TreeNode root){
        List<TreeNode> result=new LinkedList();
        Queue<TreeNode> nodeQueue=new LinkedList();
        TreeNode node=null;
        nodeQueue.add(root);
        while(!nodeQueue.isEmpty()){
            node=nodeQueue.poll();
            if(node.left==null){
                if(node.right==null){
                    result.add(node);
                }else{
                    nodeQueue.add(node.right);
                }
            }else{
                nodeQueue.add(node.left);
                if(node.right!=null){
                    nodeQueue.add(node.right);
                }
            }
        }
        return result;
    }

    //主函数，用于测试
    public static void main(String[] args){
        TreeNode root=new TreeNode(0);
        root.left=new TreeNode(1);
        root.right=new TreeNode(2);
        root.left.left=new TreeNode(3);
        root.left.right=new TreeNode(4);
        root.right.left=new TreeNode(5);
        root.right.right=new TreeNode(6);
        Leaf leaf=new Leaf();
        System.out.println(leaf.getLeaf(root));
    }
}