MD环和图的算法

defend the castle

#include <stdio.h>
#include <malloc/malloc.h>

typedef struct node {
    int data;
    struct node* next;
    struct node* pre;
} Node;


int normalvalid(Node* from,Node* to)
{
    int valid = 1;
    
    int max = 0;
    Node*p = from->next;
    max = p->data;
    while (p->data <= from->data && p!=to) {
        if (p->data > max) max = p->data;
         p = p->next;
    }
    if (p == to && to->data >max) valid = 1;
    else valid = 0;
    return valid;
}

int reversevalid(Node* from,Node* to)
{
    int valid = 1;
    int max = 0;
    Node*p = from->pre;
    max = p->data;
    
    while (p->data <= from->data && p!=to) {
        if (p->data > max)max = p->data;
         p = p->pre;
    }
    
    if (p == to && to->data >max) valid =  1;
    else valid =  0;
    return valid;
    
}


int scan(Node* head)
{
    
    int num = 0;
    Node* start = head;
    Node* next = start->next->next;

    while (start->next != head) {
        while (next != start->pre) {
            if (normalvalid(start, next) || reversevalid(next, start))
                num ++;
            next = next->next;
        }
        start = start->next;
    }
    
    next = start->next->next;
    while (next != start->pre) {
        if (normalvalid(start, next) || reversevalid(next, start))
            num ++;
        next = next->next;
    }
    start = start->next;
    
    return num;
}


int main(int argc, const char * argv[]) {
    Node* head=(Node*)malloc(sizeof(Node));;
    Node* pre;
    Node* next = NULL;
    int n;
    pre = head;
    scanf("%d",&n);
    int data;
    for (int i = 0 ; i < n; i ++) {
        scanf("%d",&data);
         pre->data = data;
        if (data && i <n-1 ) {
            next = (Node*)malloc(sizeof(Node));
             pre->next = next;
            next->pre = pre;
            pre = next;
        }
    }

    next->next =  head;
    head->pre = next;
    printf("%d",n + scan(head));
    return 0;
}