树的广度优先遍历（非递归）和深度优先遍历

今天用java写数据结构，算是涨姿势了。。。

package leetcode.test;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import java.util.Scanner;public class MaxSum {public static void main(String[] args) {MaxSum ms = new MaxSum();TreeNode root = ms.initTree();//ms.printTree(root);ms.printBroadTree(root);}//该方法返回树的头结点//首先写树的广度优先遍历public TreeNode initTree(){TreeNode root = null; //这是根元素return createNode(root);}public TreeNode createNode(TreeNode tn){int temp;System.out.print("请输入：");Scanner scanner = new Scanner(System.in);temp = scanner.nextInt();if (temp != 0){tn = new TreeNode();tn.value = temp;tn.lchild = createNode(tn.lchild); //在java中你只能通过参数将一个值传进一个函数，然而你是不能通过参数将一个值带出来的tn.rchild = createNode(tn.rchild);return tn;}else {tn = null;return null;}}public void printTree(TreeNode tn){if (tn != null){System.out.print("  "+tn.value);printTree(tn.lchild);printTree(tn.rchild);}}public void printBroadTree(TreeNode tn){List<TreeNode> list = new ArrayList<>(); //这个数组用作堆栈List<TreeNode> removeList = new ArrayList<>(); //这里存储的是要要删除的元素，因为已经访问过Iterator<TreeNode> iterator;TreeNode temp = null;if (tn != null){list.add(tn);}//我感觉下面这句话很关键，如果你要是while(list.size()!=0) ,那么下面有list.add()和list.remove()方法都在改变着list.size（）的值int count = list.size();while (count != 0){for (int i=0; i<count; i++){temp = list.get(i);System.out.print(temp.value + "  ");removeList.add(temp);if (temp.lchild != null){list.add(temp.lchild);}if (temp.rchild != null){list.add(temp.rchild);}}for (int i=0; i<removeList.size(); i++){  //将兄弟节点访问完，一并删除list.remove(removeList.get(i));}count = list.size();}}}