/*求二叉树中距离最远的两个点 * 基本思路： * 递归计算两棵树的最大高度，设置一个全局变量，距离最远的两个节点element * 其中：在计算左子支，直接刷新上述全局变量，在计算右边子支时，设置两个临时Node变量，变量里的element用于 * 保存右边子支的两个最远距离。根据比较两个距离的大小、其父节点所在的树三个的大小，来重新刷新全局变量。 * 一个Trick~：在计算子支的最远距离的时候，因为要和其父节点所在的树比较大小，保存子支的最大距离的点数。  */public class MaxLenTree {    public Node root;    public int len = 0;    public class Node {        char element;        int hight;        Node left;        Node right;        public Node(char element, int hight, Node left, Node right) {            this.element = element;            this.hight = hight;            this.left = left;            this.right = right;        }        Node() {        }    }    MaxLenTree() {/*        Node e = new Node(‘e‘, 0, null, null);        Node d = new Node(‘d‘, 0, e, null);        Node f = new Node(‘f‘, 0, null, null);        Node c = new Node(‘c‘, 0, d, f);        Node b = new Node(‘b‘, 0, c, null);        Node a = new Node(‘A‘, 0, b, null);*/        Node m = new Node(‘m‘, 0, null, null);        Node n = new Node(‘n‘, 0, null, null);        Node k = new Node(‘k‘, 0, m, n);        Node l = new Node(‘l‘, 0, null, null);        Node i = new Node(‘i‘, 0, null, null);        Node j = new Node(‘j‘, 0, k, l);        Node q = new Node(‘q‘, 0, null, null);        Node p = new Node(‘P‘, 0, q, null);        Node h = new Node(‘h‘, 0, p, null);        Node d = new Node(‘d‘, 0, h, null);        Node e = new Node(‘e‘, 0, i, j);        Node b = new Node(‘B‘, 0, d, e);        Node f = new Node(‘f‘, 0, null, null);        Node g = new Node(‘g‘, 0, null, null);        Node c = new Node(‘c‘, 0, f, g);        Node a = new Node(‘A‘, 0, b, c);        root = a;    }    public static void main(String[] args) {        MaxLenTree mTree = new MaxLenTree();        mTree.calculateHight();        mTree.run();    }    public void run() {        Node node = new Node();        System.out.println(findMaxLen(this.root, node));        System.out.println("maxNode left.element---" + maxNodeleft.element);        System.out.println("maxNoderight.element---" + maxNoderight.element);    }    public Node maxNodeleft = new Node();    public Node maxNoderight = new Node();    public int findMaxLen(Node root, Node LongestChild) {        System.out.println(LongestChild.element);        if (root.left == null && root.right == null) {            LongestChild.element = root.element;            maxNodeleft.element = root.element;            maxNoderight.element = root.element;            return 0;        }        Node leftLongestChild = new Node();        Node rightLogestChild = new Node();        if (root.left == null || root.right == null) {            if (root.right == null) {                int a = findMaxLen(root.left, leftLongestChild);                System.out.println(leftLongestChild.element);                if (hight(root) > a) {                    LongestChild.element = leftLongestChild.element;                    this.maxNodeleft.element = leftLongestChild.element;                    this.maxNoderight.element = root.element;                    return hight(root);                } else {                    LongestChild.element = leftLongestChild.element;                    return a;                }            } else {                int a = findMaxLen(root.right, rightLogestChild);                if (hight(root) > a) {                    LongestChild.element = rightLogestChild.element;                    this.maxNodeleft.element = root.element;                    this.maxNoderight.element = rightLogestChild.element;                    return hight(root);                } else {                    LongestChild.element = rightLogestChild.element;                    return a;                }            }        }        int a = findMaxLen(root.left, leftLongestChild);        Node rightNodetempLeft = new Node();        rightNodetempLeft.element = maxNodeleft.element;        Node rightNodetempRight = new Node();        rightNodetempRight.element = maxNoderight.element;        int b = findMaxLen(root.right, rightLogestChild);        int c = Math.max(a, b);        if (a > b) {            maxNodeleft.element = rightNodetempLeft.element;            maxNoderight.element = rightNodetempRight.element;        }        if (c == b) {            LongestChild.element = rightLogestChild.element;        } else {            LongestChild.element = leftLongestChild.element;        }        int d = hight(root.left) + hight(root.right) + 2;        if (c < d) {            maxNodeleft.element = leftLongestChild.element;            maxNoderight.element = rightLogestChild.element;        }        System.out.println(LongestChild.element);        return Math.max(c, d);    }    public int hight(Node root) {        if (root == null) {            return -1;        }        return root.hight;    }    public void showTree(Node root) {        if (root == null) {            return;        }        System.out.println(root.element + "<----->" + root.hight);        showTree(root.left);        showTree(root.right);    }    public void calculateHight() {        calculateHight(this.root);    }    public int calculateHight(Node root) {        if (root == null) {            return -1;        }        if (root.right == null && root.left == null) {            root.hight = 0;            return 0;        }        int temp = Math.max(calculateHight(root.left),                calculateHight(root.right)) + 1;        root.hight = temp;        return temp;    }}