解答:
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 nullptr;
}
// 選擇任意一箇中間位置數字作爲根節點
int mid = (left + right + rand() % 2) / 2;
TreeNode* root = new TreeNode(nums[mid]);
root->left = helper(nums, left, mid - 1);
root->right = helper(nums, mid + 1, right);
return root;
}
};
理解new,delete,內存泄露間關係。