算法第十周解题

108. Convert Sorted Array to Binary Search Tree

Given an array where elements are sorted in ascending order, convert it to a height balanced BST.

解题思路：  int mid = (begin + end) / 2;

/**
 * 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* sortedArrayToBST(vector<int>& nums) {
        TreeNode* root =NULL;
        if(nums.size() == 0) return NULL;
        BSTreeCons(nums, 0, nums.size() - 1, root);
        return root;
    }
    void BSTreeCons(vector<int>& nums, int begin, int end, TreeNode*& root){
        if(begin > end) return;
        int mid = (begin + end) / 2;
        root = new TreeNode(nums[mid]);
        BSTreeCons(nums, begin, mid - 1, root -> left);
        BSTreeCons(nums, mid + 1, end, root -> right);
        
    }
};

结果如下：