我米试图通过评分排序节点。我不知道我有什么错误 [英] I m trying to sort the node by score. I do not know what error i am having

问题描述

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>

struct student{
char firstname[20];
char lastname[20];
double grade;
char zipcode[10];
struct student *next;
};

void display(struct student *first)
{
while (first != NULL)
{
    printf("\nFirst name: %s", first->firstname);
    printf("\tLast name: %s", first->lastname);
    printf("\tGrade: %.2f", first->grade);
    printf("\t ZipCode: %s", first->zipcode);
    first = first->next;
}
}


/*void add_Record(struct student *first)
{
char r[20];
struct student *t;
t = first;

while (t != NULL)
{
    if (t == NULL)
    {
        first = (struct student*)malloc(sizeof(struct student));
        printf("\nEnter the first name of the student:");
        scanf("%s", first->firstname);
        printf("\nEnter the last name of the student:");
        scanf("%s", first->lastname);
        printf("\nEnter the score of the student:");
        scanf("%lf", &first->grade);
        printf("\nEnter the zipcode of the student:");
        scanf("%s", first->zipcode);
    }
}
}

void del()
{
struct student *back, *t, *k;
char r[10];
int flag = 0;
printf("\nEnter the last name of student  you want to delete:");
scanf("%s", r);
if (strcmpi(r, first->lastname) == 0)
{
    first = first->next;
    flag = 1;
}
else
{
    back = first;
    k = first->next;
    while (k != NULL)
    {
        if (strcmpi(r, k->lastname) == 0)
        {
            back->next = k->next;
            flag = 1;
            break;
        }
    }
}
if (flag == 0)
    printf("\nThe element not found!!!");
}
*/

void search(struct student *first)
{
char r[10];
int flag = 0;
printf("\nEnter the zipcode you want to search:");
scanf("%s", r);
struct student *t;
t = first;
while (t != NULL)
{
    if (strcmp(r, t->zipcode) == 0)
    {
        printf("\nFirst name: %s", t->firstname);
        printf("\tLast name: %s", t->lastname);
        printf("\tGrade: %.2f", t->grade);
        printf("\t ZipCode: %s", t->zipcode);
        flag = 1;
        break;
    }t = t->next;
}
if (flag == 0)
    printf("\nThe zipcode not in database!!");
}

void sort(struct student *first)
{
struct student *temp;
temp = NULL;
while (first != NULL)
{
    if (first-> grade > first->next->grade)
    {
        strcpy(temp->firstname, first->firstname);
        strcpy(temp->lastname, first->lastname);
        temp->grade = first->grade;
        strcpy(temp->zipcode, first->zipcode);
        strcpy(first->firstname, first->next->firstname);
        strcpy(first->lastname, first->next->lastname);
        first->grade = first->next->grade;
        strcpy(first->zipcode, first->next->zipcode);
        strcpy(first->next->firstname, temp->firstname);
        strcpy(first->next->lastname, temp->lastname);
        first->next->grade = temp->grade;
        strcpy(first->next->zipcode, temp->zipcode);
        break;
    }
}
printf("\nThe sorted record by score are: \n");
display(first);
}

int main(void)
{
struct student *first = NULL, *last = NULL;
struct student *temp;
int n;
printf("\nEnter the number of student:");
scanf("%d", &n);
int i;
for (i = 0; i < n; i++)
{
    temp = (struct student*)malloc(sizeof(struct student));
    printf("\nEnter the first name of the student:");
    scanf("%s", temp->firstname);
    printf("\nEnter the last name of the student:");
    scanf("%s", temp->lastname);
    printf("\nEnter the grade of the student:");
    scanf("%lf", &temp->grade);
    printf("\nEnter the zipcode of the student:");
    scanf("%s", temp->zipcode);
    temp->next = first;
    first = temp;
}
int o;
o = 1;
while (o != 0)
{
    printf("\nMENU\n");
    printf("\nEnter 1 for displaying database.");
    printf("\nEnter 2 for inserting an record.");
    printf("\nEnter 3 for deleting a record by lastname.");
    printf("\nEnter 4 for searching a record by zipcode.");
    printf("\nEnter 5 for sorting record by score.");
    printf("\nEnter 0 for exit!");
    printf("\nEnter the choice:");
    scanf("%d", &o);
    switch (o)
    {
    case 1:display(first); break;
        /*case 2:insertafter(*first); break;
    case 3:del(); break;*/
    case 4:search(first); break;
    case 5: sort(first); break;
    case 0:exit(0); break;
    default:printf("\nYou have entered a wrong choice!!!");
    }
}
}

问题是，如何按评分分值进行排序。我的code似乎是正确的，但不能正常工作。我做了一个临时结构，并试图交换值，但它不工作。我在做循环错了吗？或者我所有的code是错的？

The problem is that how do i sort the scores by score. My code seems right but doesn't work. I made a temp structure and tried to swap values but it doesn't work. Am i doing the loop wrong? Or all my code is wrong?

推荐答案

下面两个答案的问题

第一个排由泡沫节点链表中的节点对它们进行排序，重新排列链表

First one sorts the nodes in the node linked list by bubble sorting them, rearranging the linked list

第二行走链表，拷贝的指针每一个到一个数组，然后通过使用该结构分级部件进行排序的数组，链表不变

Second one walks the linked list, copies a pointer to each one into an array and then sorts the array by using the struct grade members, the linked list remains unchanged

#include<stdio.h>
#include<stdlib.h>
#include <string.h>

#define SWAP(T,x,y) {T *p = &(x); T *q = &(y); T z = *p; *p = *q; *q = z;}

struct student{
    char firstname[20];
    char lastname[20];
    double grade;
    char zipcode[10];
    struct student *next;
};

struct student *head=NULL;

void add(char *f, char *s, double score) {
struct student *a;
a=(struct student*)malloc(sizeof(struct student));
strcpy(a->firstname,f);
strcpy(a->lastname,s);
a->grade = score;
a->next = head;
head = a;
}
void printout(char *label) {
    struct student *node;
    printf("%s\n",label);
    for(node=head; node !=NULL; node=node->next) {
        printf("%s %s %f\n", node->firstname, node->lastname, node->grade);
    }
}

int main(int argc, char ** argv){
    int mark=8;
    struct student *walk, *prev; 
    add("Bob","Smith",10);
    add("Eric","Von Däniken",90);
    add("Morris","Minor",91);
    add("Master","Bates",9);
    add("Zoe","Bodkin",20);
    add("Mary","Pippin",30);
/* bubble sort */
printout("before");
        prev=head;
        while(mark) {
            mark=0;
        for(walk=head; 
        walk != NULL; 
        walk=walk->next) {
            if (walk->next && walk->grade > walk->next->grade) {
                /* printf("swapping %s %s\n", walk->firstname, walk->next->firstname); */
                mark=1;
                if (walk == head) {
                   struct student *v2=walk->next;
                   struct student *v3=walk->next->next;
                   SWAP(struct student *, v3->next, v2->next);
                   SWAP(struct student *, head, v3->next);
                   walk = v3;
                } else { 
                   struct student *v1=prev;
                   struct student *v2=walk;
                   struct student *v3=walk->next;
                   SWAP(struct student *, v3->next, v2->next);
                   SWAP(struct student *, v1->next, v3->next);
                   walk = v3;
                } 
            } 
            prev=walk;
        }

        }
        printout("after");
    return 0;
}

第二个版本，使用的qsort，保留链接列表的顺序

second version, uses qsort, retains linked list order

#include<stdio.h>
#include<stdlib.h>
#include <string.h>

struct student{
    char firstname[20];
    char lastname[20];
    double grade;
    char zipcode[10];
    struct student *next;
};

struct student *head=NULL;
size_t nodecount=0;

void add(char *f, char *s, double score) {
struct student *a;
a=(struct student*)malloc(sizeof(struct student));
strcpy(a->firstname,f);
strcpy(a->lastname,s);
a->grade = score;
a->next = head;
head = a;
nodecount++;
}


static int cmpgrade(const void *p1, const void *p2) {
    struct student *g1, *g2;
    g1=*(struct student **)p1;
    g2=*(struct student **)p2;
    return g1->grade > g2->grade;
}

int main(int argc, char ** argv){
    int i;
    struct student *walk,**sa, **sap; 
    add("Bob","Smith",10);
    add("Eric","Von Däniken",90);
    add("Morris","Minor",91);
    add("Master","Bates",9);
    add("Zoe","Bodkin",20);
    add("Mary","Pippin",30);

/*copy into array of pointers*/
sa=calloc(sizeof (struct student*), nodecount);
sap=sa;
        for(walk=head; walk != NULL; walk=walk->next) {
              *sap = walk;
              sap++;
        }
        printf("before\n");
        for (i=0; i< nodecount; i++) {
            printf("%s %s %f\n", sa[i]->firstname, sa[i]->lastname, sa[i]->grade);
        }
        /* qsort */
        qsort(sa, nodecount, sizeof (struct student *), cmpgrade);

        printf("after\n");
        for (i=0; i< nodecount; i++) {
            printf("%s %s %f\n", sa[i]->firstname, sa[i]->lastname, sa[i]->grade);
        }
    return 0;
}

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