654. Maximum Binary Tree

Given an integer array with no duplicates. A maximum tree building on this array is defined as follow:

1. The root is the maximum number in the array.
2. The left subtree is the maximum tree constructed from left part subarray divided by the maximum number.
3. The right subtree is the maximum tree constructed from right part subarray divided by the maximum number.

Construct the maximum tree by the given array and output the root node of this tree.

Example 1:

Input: [3,2,1,6,0,5]

Output: return the tree root node representing the following tree:

      6

    /   \

   3     5

    \    /

     2  0  

       \

        1

Note:The size of the given array will be in the range [1,1000].

做出来了 但是做复杂了 左右子树并不需要分开搞 犯这种错误很多次了

    public TreeNode constructMaximumBinaryTree(int[] nums) {
        return construct(nums, 0, nums.length);
    }

    public TreeNode construct(int[] nums, int l, int r) {
        if (l == r)
            return null;
        int max_i = max(nums, l, r);
        TreeNode root = new TreeNode(nums[max_i]);
        root.left = construct(nums, l, max_i);
        root.right = construct(nums, max_i + 1, r);
        return root;
    }

    public int max(int[] nums, int l, int r) {//找最大值
        int max_i = l;
        for (int i = l; i < r; i++) {
            if (nums[max_i] < nums[i])
                max_i = i;
        }
        return max_i;
    }