654. Maximum Binary Tree

最新推荐文章于 2022-11-14 20:37:17 发布

转载最新推荐文章于 2022-11-14 20:37:17 发布 · 54 阅读

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原文链接：http://www.cnblogs.com/jxr041100/p/8035979.html

本文介绍了一种基于给定整数数组构建最大二叉树的方法。该树的根节点为数组中的最大值，左右子树则分别由除去最大值后的左右部分数组递归构建而成。文章提供了完整的C++实现代码。

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

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* constructMaximumBinaryTree(vector<int>& nums) {
        int n = nums.size();
        return dfs(0,n-1,nums);
    }
    TreeNode *dfs(int left,int right,vector<int>&nums)
    {
        if(left>right) return NULL;
        int idx = find_max(left,right,nums);
        TreeNode *root = new TreeNode(nums[idx]);
        root->left = dfs(left,idx-1,nums);
        root->right = dfs(idx+1,right,nums);
        return root;
        
    }
    int find_max(int left,int right,vector<int>& nums)
    {
        int max_num = INT_MIN;
        int res;
        for(int i = left;i<=right;i++)
        {
            if(nums[i]>max_num)
            {
               max_num = nums[i];
                res = i;
            }
        }
        return res;
    }
};

转载于:https://www.cnblogs.com/jxr041100/p/8035979.html