c_cpp 在链表中查找循环的长度

Posted 2021-05-14

//https://www.geeksforgeeks.org/find-length-of-loop-in-linked-list/
#include<iostream>
#include<list>
using namespace std;

struct linked_list {
    int data;
    struct linked_list* next;
};
typedef struct linked_list node;

node* insert(node* head, int n) {
    node* list = (node*)malloc(sizeof(node*));
    list->data=n;
    list->next=head;
    head=list;
    return head;
}

int CountLoop (node* n) {
    int len = 1;
    node* temp = n;
    while (temp->next != n){
        len++;
        temp = temp->next;
    }
    return len;
}

int DetectLoop (node* head) {
    node *slow=head, *fast=head,*ptr;
    while (slow && fast && fast->next) {
        slow = slow->next;
        fast = fast->next->next;

        if (slow == fast)
            return CountLoop (slow);
    }
}

int main() {
    int n;
    node* head = NULL;
    while (true) {
        cout<< "Enter the element, enter -9 to stop: ";
        cin>>n;
        if (n==-9)
            break;
        else
            head = insert(head,n);
    }
    head->next->next->next->next->next = head->next;
    cout<< "Length of Loop is " << DetectLoop(head);
}