Linked list OJ - next

---

Preface

1. Linked list segmentation

Niuke.com CM11: Linked list segmentation - - - Click here to send

Solution:
Idea map:

Code:

2. Circular linked list I

Likou 141: Ring Linked List - - - Click here to send

Idea map:

Extended questions:

Code:

bool hasCycle(struct ListNode *head) {
    
    
    struct ListNode*fast=head,*slow=head;
    while(fast && fast->next)
    {
    
    
    	//slow走一步
        slow=slow->next;
        //fast走两步
        fast=fast->next->next;
        //若相等（相遇）则有环，返回true并退出程序
        if(fast==slow)
        {
    
    
            return true;
        }
    }
    //否则无环
    return false;
}

3. Circular Linked List II

Likou 142: Ring Linked List II- - - Click here to send

Solution:
Idea map:

Code:

struct ListNode *detectCycle(struct ListNode *head) {
    
    
    struct ListNode*fast=head;
    struct ListNode*slow=head;
    while(fast && fast->next)
    {
    
    
        slow=slow->next;
        fast=fast->next->next;
        if(fast==slow)
        {
    
    
            struct ListNode*meet=slow;
            while(head != meet)
            {
    
    
                head=head->next;
                meet=meet->next;
            }
            return meet;
        }
    }
    return NULL;
}

4. Palindrome structure of linked list

Niuke.com OR36: Palindrome structure of linked list - - - Click here to send

Idea map:

Code:

struct ListNode*reverseList(struct ListNode*head)
    {
    
    
        struct ListNode*cur=head;
        struct ListNode*newhead=NULL;
        while(cur)
        {
    
    
            struct ListNode*next=cur->next;
            cur->next=newhead;
            newhead=cur;
            cur=next;
        }
        return newhead;
    }
    struct ListNode*middleNode(struct ListNode*head)
    {
    
    
        struct ListNode*slow=head;
        struct ListNode*fast=head;
        while(fast && fast->next)
        {
    
    
            slow=slow->next;
            fast=fast->next->next;
        }
        return slow;
    }
    bool chkPalindrome(ListNode* head) {
    
    
        struct ListNode*mid=middleNode(head);
        struct ListNode*rhead=reverseList(mid);
        while(head && rhead)
        {
    
    
            if(head->val != rhead->val)
                return false;
            head=head->next;
            rhead=rhead->next;
        }
        return true;
    }

5. Copy of random linked list

Likou 138: Copy of Random Linked List - - - Click here to send

Idea Map:

Code:

struct Node* copyRandomList(struct Node* head) 
{
    
    
	struct Node*cur=head;
    while(cur)
    {
    
    
        struct Node*copy=(struct Node*)malloc(sizeof(struct Node));
        copy->val=cur->val;

        copy->next=cur->next;
        cur->next=copy;

        cur=copy->next;
    } 
    cur=head;
    while(cur)
    {
    
    
        struct Node*copy=cur->next;
        if(cur->random==NULL)
        {
    
    
             copy->random=NULL;
        }
           
        else
        {
    
    
            copy->random=cur->random->next;
        }
            
        cur=copy->next;
    }
    cur=head;
    struct Node*newhead=NULL;
    struct Node*tail=NULL;
    while(cur)
    {
    
    
        struct Node*copy=cur->next;
        struct Node*next=copy->next;
        if(tail==NULL)
        {
    
    
            newhead=tail=copy;
        }
        else
        {
    
    
            tail->next=copy;
            tail=tail->next;
        }
        cur->next=next;
        cur=next;
    }
    return newhead;
}