C language actually comes with qsort function

Quick sort is one of the most used sorting algorithm, I have detailed review before, in the C standard library actually has a quick sort function, let’s talk about the details of usage.

The qsort function is contained in

void qsort(void * base,size_t nmemb,size_t size ,int(*compar)(const void *,const void *));

Parameter Description:

1.base, the array to sort;

2.nmemb, the number of elements in the array;

3.size, the memory space occupied by each array element can be obtained using the sizeof function

4.compar, the pointer to the function pointer function. This function is used to compare two array elements, the first parameter is greater than, equal to, less than the second parameter, respectively, showed positive, zero, negative.

Here are a few examples:

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

void main(void)
{
int i;
int a[10]={0,1,2,3,4,5,6,7,8,9};
char b[10]={'a','b','c','d','e','f','g','h','i','j'};
double c[10]={0.1,0.2,0.9,0.5,0.3,0.6,0.7,0.8,1.1,1.2};
int cmp1(const void * a,const void * b)
{
return (*(int*)a-*(int*)b);//a>b Return positive
}
int cmp2(const void * a,const void *b)
{
return(*(char*)a-*(char*)b);
}
int cmp3(const void * a,const void * b)
{
if(fabs(*(double*)a-*(double *)b)<1*exp(-20)) return 0;
else return(((*(double*)a-*(double*)b)>0)?1:-1);
}
qsort(a,10,sizeof(int),&cmp1);
/*For function pointers (pointers to functions), it is possible to directly pass
in the function name and the function name for the & operation because the function
address is also taken when the function is called*/
qsort(b,10,sizeof(char),cmp2);
qsort(c,10,sizeof(double),cmp3);
for(i=0;i<10;i++)
printf("%d ",a[i]);
for(i=0;i<10;i++)
printf("%c ",b[i]);
for(i=0;i<10;i++)
printf("%lf ",c[i]);
}