题目链接

递归 + 二叉树

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    public TreeNode constructMaximumBinaryTree(int[] nums) {
        return traversal(nums,0, nums.length - 1);
    }

    public TreeNode traversal(int[] nums,int left,int right){
        if(left > right){
            return null;
        }

        int maxIndex = left;
        for(int i = left + 1; i <= right; i++){
            if(nums[i] > nums[maxIndex]){
                maxIndex = i;
            }
        }

        TreeNode node = new TreeNode(nums[maxIndex]);

        node.left = traversal(nums,left,maxIndex - 1);
        node.right = traversal(nums,maxIndex + 1,right);

        return node;
    }
}