求二叉树中节点的最大距离递归解法

问题定义

如果我们把二叉树看成一个图，父子节点之间的连线看成是双向的，我们姑且定义"距离"为两节点之间边的个数。写一个程序求一棵二叉树中相距最远的两个节点之间的距离。

代码实现中二叉树用的是完全二叉树

import java.util.LinkedList;public class Test_3_8 {public static int maxlen=0;public static void main(String[] args) {BTree btree = new BTree();int[] arr={1,2,3,4,5};for(int i =0;i<arr.length;i++){TreeNode newnode = new TreeNode();newnode.setValue(i);newnode.setMaxleft(0);newnode.setMaxright(0);btree.insertnode(newnode);}FindMaxLen(btree.getTree().getRoot());System.out.println(maxlen);}//寻找树中最长的两段距离public static void FindMaxLen(TreeNode root){//遍历到叶子节点，返回if(root==null)return;//如果左子树为空，那么该节点的左边最长距离为0if(root.getLeftchild()==null)root.setMaxleft(0);//如果右子树为空，那么该节点的右边最长距离为0if(root.getRightchild()==null)root.setMaxright(0);//如果左子树不为空，递归寻找左子树的最长距离if(root.getLeftchild()!=null)FindMaxLen(root.getLeftchild());//如果右子树不为空，递归寻找右子树的最长距离if(root.getRightchild()!=null)FindMaxLen(root.getRightchild());//计算左子树最长节点距离if(root.getLeftchild()!=null){int tempmax=0;if(root.getLeftchild().getMaxleft()>root.getLeftchild().getMaxright())tempmax=root.getLeftchild().getMaxleft();elsetempmax=root.getLeftchild().getMaxright();root.setMaxleft(tempmax+1);}//计算右子树最长节点距离if(root.getRightchild()!=null){int tempmax=0;if(root.getRightchild().getMaxleft()>root.getRightchild().getMaxright())tempmax=root.getRightchild().getMaxleft();elsetempmax=root.getRightchild().getMaxright();root.setMaxright(tempmax+1);}//更新最长距离if(root.getMaxleft()+root.getMaxright()>maxlen){maxlen=root.getMaxleft()+root.getMaxright();}}}class TreeNode{private TreeNode leftchild;//左子树private TreeNode rightchild;//右子树private int maxleft;//左子树中的最长距离private int maxright;//右子树中的最长距离private int value;//该节点的值public int getValue() {return value;}public void setValue(int value) {this.value = value;}public TreeNode getLeftchild() {return leftchild;}public void setLeftchild(TreeNode leftchild) {this.leftchild = leftchild;}public TreeNode getRightchild() {return rightchild;}public void setRightchild(TreeNode rightchild) {this.rightchild = rightchild;}public int getMaxleft() {return maxleft;}public void setMaxleft(int maxleft) {this.maxleft = maxleft;}public int getMaxright() {return maxright;}public void setMaxright(int maxright) {this.maxright = maxright;}}class Tree{private TreeNode root;public TreeNode getRoot() {return root;}public void setRoot(TreeNode root) {this.root = root;}}class Queue1{private LinkedList<TreeNode> list;public Queue1(){this.list=new LinkedList<TreeNode>();}public void push(TreeNode node){list.add(node);}public TreeNode pop(){return list.removeFirst();}public boolean isEmpty(){return list.isEmpty();}}class BTree{private Tree tree;public Tree getTree() {return tree;}public void setTree(Tree tree) {this.tree = tree;}private Queue1 queue;public BTree(){this.tree=new Tree();}public void insertnode(TreeNode node){if(tree.getRoot()==null){tree.setRoot(node);return;}else{Queue1 queue=new Queue1();queue.push(tree.getRoot());while(!queue.isEmpty()){TreeNode temp = queue.pop();if(temp.getLeftchild()==null){temp.setLeftchild(node);return;}else if(temp.getRightchild()==null){temp.setRightchild(node);return;}else{queue.push(temp.getLeftchild());queue.push(temp.getRightchild());}}}}}