题解 | #将升序数组转化为平衡二叉搜索树#

/**
 * struct TreeNode {
 *	int val;
 *	struct TreeNode *left;
 *	struct TreeNode *right;
 * };
 */

class Solution {
public:
    /**
     * 
     * @param num int整型vector 
     * @return TreeNode类
     */
    TreeNode* function(vector<int>& num, int l, int r) {
        if(r - l < 1)
            return nullptr;
        int mid = (l + r) / 2;
        TreeNode* root = new TreeNode(num[mid]);
        root->left = function( num, l, mid); // 生成左子树
        root->right = function( num, mid + 1, r); // 生成右子树
        return root;
        
    }
    TreeNode* sortedArrayToBST(vector<int>& num) {
        // write code here
        int n = num.size();
        if(n < 1)
            return nullptr;
        TreeNode* root; // 生成根节点
        root = function(num, 0, n);
        return root;
    }
};