查找二叉树最大值节点

如题 : 在二叉树中查找最大值的节点并返回

测试数据 : {1,-5,3,1,2,-4,-5}

答案 : 3

思路 : 从根节点往下分别查找左子树和右子树的最大节点，再比较左子树，右子树，根节点的大小得到结果，在得到左子树和右子树最大节点的过程相似，因此可以采用递归的方法

//树节点结构public class TreeNode {TreeNode left;TreeNode right;int val;TreeNode(int val){this.val = val;}}public class Solution {/** * @param root 传入根节点 * @return 返回最大结果 */public static TreeNode maxNode(TreeNode root){//当再无子节点，返回当前节点if (root == null) {return root;} TreeNode left = maxNode(root.left);//递归得到左子树最大值TreeNode right = maxNode(root.right);//递归得到右子树的最大值return max(root,max(left,right));//返回左节点，根节点,右节点的最大值}public static TreeNode max(TreeNode a,TreeNode b) {if (a == null) {return b;}if (b == null) {return a;}if (a.val > b.val) {return a;}return b;}public static void main(String[] args) {TreeNode t1 = new TreeNode(1);TreeNode t2 = new TreeNode(-5);TreeNode t3 = new TreeNode(3);TreeNode t4 = new TreeNode(1);TreeNode t5 = new TreeNode(2);TreeNode t6 = new TreeNode(-4);TreeNode t7 = new TreeNode(-5);t1.left = t2;t1.right = t5;t2.left = t3;t2.right = t4;t5.left = t6;t5.right = t7;System.out.println(Solution.maxNode(t1).val);}}