算法

(树、DFS)

每次选择一个区间的中点作为当前区间的根，然后对左右子树依次构造。

C++ 代码

class Solution {
public:
    TreeNode* sortedArrayToBST(vector<int>& nums) {
        return helper(nums, 0, nums.size() - 1);
    }

    TreeNode *helper(vector<int> &nums, int left, int right) {
        if (left > right) { return NULL; }
        int aMid = (left + right) / 2;
        TreeNode *aRoot = new TreeNode(nums[aMid]);
        aRoot->left = helper(nums, left, aMid - 1);
        aRoot->right = helper(nums, aMid + 1, right);
        return aRoot;
    }
};