[英]Sorting dynamic array in a structure with C qsort ()
我在结构中对数组(动态分配)进行排序时遇到问题。 首先,想法是将数组i在结构中以升序排列。 然后,我在考虑对数组i进行排序,以保持数组j与其构造初始结构时所获得的“关系”相同。 我尝试为第一个想法工作,但是使用qsort却没有任何结果。所以这是我的代码...有什么想法吗? 我认为比较功能的构造存在问题。
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
int M =10;
int N =30;
int K = 10;
struct element {
int *i;
int *j;
int k;
};
struct element *create_structure();
void print_element(struct element *);
int compare (const void *, const void * );
struct element * sort(struct element *);
main()
{
srand(time(NULL));
struct element *lista;
int count;
lista=create_structure();
print_element(lista);
printf("\n");
lista=sort(lista);
}
struct element *create_structure()
{
int aux1,aux2,count,load;
struct element *structure;
structure = (struct element *) malloc (M*sizeof(struct element *));
structure->k=K;
structure->i= (int *)malloc(structure->k*sizeof(int));
structure->j=(int *)malloc (structure->k*sizeof(int));
for (count = 0; count < K; count ++)
{
aux1=rand()%N;
(structure->i)[count]=aux1;
do
{
aux2=rand()%N;
}while(aux2==aux1);
(structure->j)[count]=aux2;
}
return (structure);
}
void print_element(struct element *lista)
{
int count;
for(count = 0; count < K; count ++)
{
printf("%d %d\n",lista->i[count],lista->j[count]);
}
}
int compare(const void *a, const void *b)
{
struct element *ia = (struct element *)a;
struct element *ib = (struct element *)b;
int *ptr1=(ia->i);
int *ptr2=(ib->i);
return (*ptr1-*ptr2);
}
struct element * sort(struct element *list)
{
qsort(list, sizeof(list->i)/ sizeof(int) , sizeof(list->i), compare);
//qsort(list->i, K, sizeof(list->i), compare);
print_element(list);
return (list);
}
很抱歉参加晚会! :)
因此,让我们首先在代码中提及错误的语句
>>首先
在函数create_structure()
您想为结构指针分配内存
struct element *structure; // here your structure pointer is
//pointing to memory space of type struct element
structure = (struct element *) malloc (M*sizeof(struct element *));
|------------------------|
|
V
Here you are allocating memory space of type struct element* which is
wrong ! instead it must be sizeof(struct element)
关于同一函数中的while循环,我发现它完全没有用
aux1=rand()%N;
(structure->i)[count]=aux1; // the value is in aux1 variable
do
{
aux2=rand()%N;
}while(aux2==aux1); // the loop try to get the same value of aux1
// or you have just stored it in aux1
(structure->j)[count]=aux2; // it is easy to delete the while loop and
// change aux2 by aux1
>>第二
关于排序
qsort(list, sizeof(list->i)/ sizeof(int) , sizeof(list->i), compare);
|-----|
|
V
It is not an adress of the array so it is Wrong !
知道了主要问题之后,便是一个基于您自己的代码的代码版本,该版本可以完美运行
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <math.h>
int M =10;
int N =30;
int K = 10;
struct element {
int *i;
int *j;
int k;
};
struct element *create_structure();
void print_element(struct element *);
int compare (const void *, const void * );
void sort(struct element *); // changed the return value of sort
// to void as the argument will be changed directly because it is a
// pointer
int main()
{
srand(time(NULL));
struct element *lista;
lista=create_structure();
printf("\n--------- i --- j ---------\n\n");
print_element(lista);
printf("\n---------------------------\n");
sort(lista);
print_element(lista);
return 0;
}
struct element *create_structure()
{
int aux1=0,count=0;
struct element *structure;
// Changed the allocation of structure pointer
structure = (struct element *) malloc (sizeof(struct element));
structure->k=K;
structure->i= (int *)malloc(K*sizeof(int));
structure->j=(int *)malloc (K*sizeof(int));
for (count = 0; count < K; count ++)
{
aux1=rand()%N;
// we kept only the first aux1 and copied it in the two arrays
(structure->i)[count]=aux1;
(structure->j)[count]=aux1;
}
return (structure);
}
void print_element(struct element *lista)
{
int count=0;
for(count = 0; count < K; count++)
{
printf("row=%2d : %2d %2d\n",count+1,(lista->i)[count],(lista->j)[count]);
}
}
int compare(const void *a, const void *b)
{
// compare the values of two case of array pointed by i of type int
return *(int*)a-*(int*)b;
}
void sort(struct element *list)
{
// we will sort the array pointed by i which contains K elements
// of type int and size sizeof(int) by using the compare function
qsort(list->i, K , sizeof(int), compare);
}
希望能帮助到你 ! :)
注意:在代码块v13.12中使用此代码会在Linux(gcc版本4.8.2)下生成错误输出! [在Code :: Blocks中可能是一个BUG],但是在gcc的命令行中使用它会给出正确的输出!
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