题目

二叉树的最大节点
在二叉树中寻找值最大的节点并返回。

样例
给出如下一棵二叉树：

1
/ \
-5 2
/ \ / \
0 3 -4 -5
返回值为 3 的节点。

解答

public class FindMaxNumInTree {

    public static void main(String[] args) {
        TreeNode treeNode1 = new TreeNode(1);
        TreeNode treeNode2 = new TreeNode(-5);
        TreeNode treeNode3 = new TreeNode(2);
        TreeNode treeNode4 = new TreeNode(0);
        TreeNode treeNode5 = new TreeNode(3);
        TreeNode treeNode6 = new TreeNode(-4);
        TreeNode treeNode7 = new TreeNode(5);

        treeNode1.left = treeNode2;
        treeNode1.right = treeNode3;
        treeNode2.left = treeNode4;
        treeNode2.right = treeNode5;
        treeNode3.left = treeNode6;
        treeNode3.right = treeNode7;

        System.out.println(maxNode(treeNode1).val);

    }

    /* * @param root: the root of tree * @return: the max node */
    public static TreeNode maxNode(TreeNode root) {
        // write your code here
        TreeNode treeNode = root;
        return  getMax(root, treeNode);
    }

    public static TreeNode getMax(TreeNode currentNode, TreeNode maxNode) {
        if (currentNode == null){
            return maxNode;
        }
        if (currentNode.val > maxNode.val) {
            maxNode = currentNode;
        }
        TreeNode leftTreeNode = getMax(currentNode.left, maxNode);
        TreeNode rightTreeNode = getMax(currentNode.right, maxNode);
        return leftTreeNode.val>rightTreeNode.val?leftTreeNode:rightTreeNode;
    }

    public static class TreeNode {
        public int      val;
        public TreeNode left, right;

        public TreeNode(int val) {
            this.val = val;
            this.left = this.right = null;
        }
    }
}