題目：

題解：

int getLength(struct ListNode* head) {int ret = 0;while (head != NULL) {++ret, head = head->next;}return ret;
}struct TreeNode* buildTree(struct ListNode** head, int left, int right) {if (left > right) {return NULL;}int mid = (left + right + 1) / 2;struct TreeNode* root = (struct TreeNode*)malloc(sizeof(struct TreeNode));root->left = buildTree(head, left, mid - 1);root->val = (*head)->val;(*head) = (*head)->next;root->right = buildTree(head, mid + 1, right);return root;
}struct TreeNode* sortedListToBST(struct ListNode* head) {int length = getLength(head);return buildTree(&head, 0, length - 1);
}