在这个程序中,它就像一个书店,有价格,相关性,星级和ID的信息, 该程序将需要根据价格(从最低到最高)对列表进行排序。该程序只需要实现一个合并排序(sort将采用compare_on_price的参数,因此它将列出从最低到最高的价格),然后接口调用接口函数的排序,最后,在它调用的main函数中接口。
项目清单如下
Stars Price Relv ID
4.5 12.49 7.9 1
5 7.99 7.6 2
2 16.99 6.2 3
2.5 15.49 9.1 4
3.5 20.99 6 5
1 9.99 8 6
1.5 13.99 1 7
5 8.49 8.3 8
3.5 10.49 5.2 9
排序后,价格应从最低到最高列出。
到目前为止的错误:
part1.c:117:20: error: expected expression before ',' token
part1.c:117:20: warning: passing argument 1 of 'mergesort' makes pointer from integer without a cast
part1.c:74:6: note: expected 'int *' but argument is of type 'int'
part1.c:117:20: warning: passing argument 4 of 'mergesort' makes pointer from integer without a cast
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
FILE *fp;
typedef struct book{
double rating;
double price;
double relevance;
int ID;
}B;
B *list;
int read_file(char* infile, int N)
{
int c;
if((fp=fopen(infile, "rb")))
{
fscanf(fp, "%*s\t%*s\t%*s\t%*s\n");
c=0;
while((!feof(fp))&&(c<N))
{
fscanf(fp, "%lf\t%lf\t%lf\t%d\n", &list[c].rating, &list[c].price, &list[c].relevance, &list[c].ID);
c++;
}
fclose(fp);
}
else
{
fprintf(stderr,"%s did not open. Exiting.\n",infile);
exit(-1);
}
return(c);
}
int comp_on_rating(const void *a, const void *b)
{
if ((*(B *)a).rating < (*(B *)b).rating)
return -1;
else if ((*(B *)a).rating > (*(B *)b).rating)
return 1;
else
return 0;
}
int comp_on_relev(const void *a, const void *b)
{
if ((*(B *)a).relevance < (*(B *)b).relevance)
return -1;
else if ((*(B *)a).relevance > (*(B *)b).relevance)
return 1;
else
return 0;
}
int comp_on_price(const void *a, const void *b)
{
if ((*(B *)a).price < (*(B *)b).price)
return 1;
else if ((*(B *)a).price > (*(B *)b).price)
return -1;
else
return 0;
}
/* Stable sorting method: if it keeps elements with equal keys in he smae
relative order as they were in te input. */
void mergesort(int a[],int low, int high, int(*compar)(const void *, const void *))
{
int i = 0;
int length = high - low + 1;
int pivot = 0;
int merge1 = 0;
int merge2 = 0;
int working[length];
if(low == high)
return;
pivot = (low + high) / 2;
mergesort(a, low, pivot,compar );
mergesort(a, pivot + 1, high,compar);
for(i = 0; i < length; i++)
working[i] = a[low + i];
merge1 = 0;
merge2 = pivot - low + 1;
for(i = 0; i < length; i++) {
if(merge2 <= high - low)
if(merge1 <= pivot - low)
if(working[merge1] > working[merge2])
a[i + low] = working[merge2++];
else
a[i + low] = working[merge1++];
else
a[i + low] = working[merge2++];
else
a[i + low] = working[merge1++];
}
} //end function.
void user_interface(int N)
{
// For Part 1 this function calls the sort function to sort on Price only
mergesort(N,0,,N-1, comp_on_price);
}
void print_results(int N)
{
int i;
if((fp=fopen("top20.txt","w")))
{
for(i=N-1;i>=N-20;i--)
{
printf("%g %g %g %d\n", list[i].rating, list[i].price, list[i].relevance, list[i].ID);
fprintf(fp, "%g %g %g %d\n", list[i].rating, list[i].price, list[i].relevance, list[i].ID);
}
fclose(fp);
}
else
{
fprintf(stderr,"Trouble opening output file top20.txt\n");
exit(-1);
}
}
int main(int argc, char *argv[])
{
int N;
if(argc!=3)
{
fprintf(stderr, "./exec <input_size> <filename>\n");
exit(-1);
}
/* top 20 for example */
N=atoi(argv[1]);
list = (B *)malloc(N*sizeof(B));
/*read the file into the n variable*/
N=read_file(argv[2], N);
user_interface(N);
print_results(N);
return(0);
}
答案 0 :(得分:1)
1
mergesort(N,0,,N-1, comp_on_price);
^
Extra , in there...
void mergesort(int a [],int low,int high,int(* compar)(const void *,const void *)) ^ ^ ^ ^ array int int function pointer
您的电话:
mergesort(N,0,,N-1, comp_on_price);
^ ^ ^ ^
int int int function name,
a function point is an address of your function