翻转链表

struct ListNode* reverseList(struct ListNode* head) {struct ListNode* prev = NULL;struct ListNode* curr = head;while (curr != NULL) {struct ListNode* nextTemp = curr->next;//nextTemp的作用是为了记录，以便再反转后可以curr->next = prev; //                                               //找到下一个结点prev = curr;curr = nextTemp;}return prev;
}

struct ListNode* midfind(struct ListNode* head) {  //用快慢指针找中间节点struct ListNode* slow = head;struct ListNode* fast = head;while (fast->next!= NULL && fast->next->next != NULL) { // 修改了循环条件slow = slow->next;fast = fast->next->next;}return slow;
}struct ListNode* reverseList(struct ListNode* head) {  //翻转链表struct ListNode* pre = NULL;struct ListNode* cur = head;while (cur != NULL) {struct ListNode* temp = cur->next;cur->next = pre;pre = cur;cur = temp;}return pre;
}struct ListNode* mergeList(struct ListNode* l1, struct ListNode* l2) { //合并链表struct ListNode dummy;struct ListNode* tail = &dummy;while (l1 != NULL && l2 != NULL) {tail->next = l1;l1 = l1->next;tail = tail->next;tail->next = l2;l2 = l2->next;tail = tail->next;}if (l1 != NULL) {tail->next = l1;} else {tail->next = l2;}return dummy.next;
}void reorderList(struct ListNode* head) {if (head == NULL)return;struct ListNode* mid = midfind(head);struct ListNode* l1 = head;struct ListNode* l2 = mid->next;mid->next = NULL;l2 = reverseList(l2);head = mergeList(l1, l2); // 修改了函数返回的用法
}

//暴力求解（时间超限）
int minSubArrayLen(int s, int* nums, int numsSize) {if (numsSize == 0) {return 0;}int ans = INT_MAX;for (int i = 0; i < numsSize; i++) {int sum = 0;for (int j = i; j < numsSize; j++) {sum += nums[j];if (sum >= s) {ans = fmin(ans, j - i + 1);break;}}}return ans == INT_MAX ? 0 : ans;
}

//滑动窗口
int minSubArrayLen(int target, int* nums, int numsSize) {int result=INT_MAX;int ans=0;int sum=0;int i=0;for(int j=0;j<numsSize;j++){sum+=nums[j];while(sum>=target){ans=j-i+1;result=fmin(result,ans);sum=sum-nums[i];i++;}}return result==INT_MAX?0:result;
}

滑动窗口讲解视频参考：【拿下滑动窗口！ | LeetCode 209 长度最小的子数组-哔哩哔哩】 https://b23.tv/q4YearN