[LC 654.最大二叉树]

递归

/**
 * 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 build(nums,0,nums.length-1);
    }

    public TreeNode build(int []nums, int lo,int hi){
        if(lo>hi)
            return null;
        int index = -1;
        int Max = Integer.MIN_VALUE;
        for(int i=lo;i<=hi;i++){
            if(nums[i]>Max){
                index = i;
                Max = nums[i];
            }
        }
        TreeNode root = new TreeNode(Max);
        root.left = build(nums,lo,index-1);
        root.right = build(nums,index+1,hi);
        return root;
    }
}