654. 最大二叉树

解法一

每次找出最大值的下标，创建结点，然后递归遍历左右子树。

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode constructMaximumBinaryTree(int[] nums) {
        if (nums.length == 0) {
            return null;
        }
        if (nums.length == 1) {
            return new TreeNode(nums[0]);
        }
        int maxIndex = 0;
        for (int i = 0; i < nums.length; ++i) {
            if (nums[i] > nums[maxIndex]) {
                maxIndex = i;
            }
        }
        TreeNode node = new TreeNode(nums[maxIndex]);
        if (maxIndex > 0) {
            node.left = constructMaximumBinaryTree(Arrays.copyOfRange(nums, 0, maxIndex));
        }
        if (maxIndex < nums.length - 1) {
            node.right = constructMaximumBinaryTree(Arrays.copyOfRange(nums, maxIndex + 1, nums.length));
        }
        return node;
    }
}