Maximum Binary Tree

题目：

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

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

解答：

利用递归解决该问题，只需要找到一组数中最大的，然后建立左子树，建立右子树即可.

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代码如下：

public class Solution {    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) {        int max_i = l;        for (int i = l; i < r; i++) {            if (nums[max_i] < nums[i])                max_i = i;        }        return max_i;    }}