LeetCode 654 最大二叉树[DFS 分治] HERODING的LeetCode之路

Posted 2022-08-23 HERODING23

解题思路：
本质上是利用分治思想解决的问题，首先找到数组的最大值生成节点，然后再分别向最大值的左右区间进行相同的操作，返回左右子节点，代码如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode 
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) 
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) 
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) 
 * ;
 */
class Solution 
public:
    TreeNode* constructMaximumBinaryTree(vector<int>& nums) 
        return construct(nums, 0, nums.size() - 1);
    

    TreeNode* construct(vector<int>& nums, int left, int right) 
        if(left > right) 
            return nullptr;
        
        int index = left;
        for(int i = left + 1; i <= right; i ++) 
            if(nums[i] > nums[index]) 
                index = i;
            
        
        TreeNode* node = new TreeNode(nums[index]);
        node->left = construct(nums, left, index - 1);
        node->right = construct(nums,index + 1, right);
        return node;
    
;