1.以函数形式实现单链表的建立、插入、删除、查找运算的思路结构。 2.以函数形式实现循环单链表的建立、插入、删除、查找运算的思路结构。

1. 单链表的建立、插入、删除、查找运算思路结构：

定义单链表节点结构体：

struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

1.1 单链表的建立

ListNode* createList(vector<int>& nums) {
    ListNode* head = new ListNode(0);
    ListNode* cur = head;
    for (int i = 0; i < nums.size(); i++) {
        ListNode* newNode = new ListNode(nums[i]);
        cur->next = newNode;
        cur = newNode;
    }
    return head->next;
}

1.2 单链表的插入

void insertNode(ListNode* head, int val) {
    ListNode* newNode = new ListNode(val);
    newNode->next = head->next;
    head->next = newNode;
}

1.3 单链表的删除

void deleteNode(ListNode* head, int val) {
    ListNode* cur = head;
    while (cur->next != NULL) {
        if (cur->next->val == val) {
            ListNode* temp = cur->next;
            cur->next = temp->next;
            delete temp;
            break;
        }
        cur = cur->next;
    }
}

1.4 单链表的查找

ListNode* searchNode(ListNode* head, int val) {
    ListNode* cur = head->next;
    while (cur != NULL) {
        if (cur->val == val) {
            return cur;
        }
        cur = cur->next;
    }
    return NULL;
}

2. 循环单链表的建立、插入、删除、查找运算思路结构：

定义循环单链表节点结构体：

struct ListNode {
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};

2.1 循环单链表的建立

ListNode* createList(vector<int>& nums) {
    ListNode* head = new ListNode(0);
    ListNode* cur = head;
    for (int i = 0; i < nums.size(); i++) {
        ListNode* newNode = new ListNode(nums[i]);
        cur->next = newNode;
        cur = newNode;
    }
    cur->next = head;
    return head->next;
}

2.2 循环单链表的插入

void insertNode(ListNode* head, int val) {
    ListNode* newNode = new ListNode(val);
    ListNode* cur = head->next;
    while (cur->next != head) {
        cur = cur->next;
    }
    newNode->next = head;
    cur->next = newNode;
    head = newNode;
}

2.3 循环单链表的删除

void deleteNode(ListNode* head, int val) {
    ListNode* cur = head;
    while (cur->next != head) {
        if (cur->next->val == val) {
            ListNode* temp = cur->next;
            cur->next = temp->next;
            delete temp;
            break;
        }
        cur = cur->next;
    }
}

2.4 循环单链表的查找

ListNode* searchNode(ListNode* head, int val) {
    ListNode* cur = head->next;
    while (cur != head) {
        if (cur->val == val) {
            return cur;
        }
        cur = cur->next;
    }
    return NULL;
}