大家都嫌麻烦不愿意做这道题吗？楼主已经研究了好几天了，谁可以帮

计算系统时间#include<stdio.h>
#include<time.h>
int main(void)
{
time_t b,e;
char timestr[80];
b=time(NULL);
strftime(timestr,79,"%H:%M:%S",localtime(&b));
puts(timestr);
puts("press ENTER...");
getchar();
e=time(NULL);
strftime(timestr,79,"%H:%M:%S",localtime(&e));
puts(timestr);
printf("%d Sec.\n",e-b);
return 0;
}

冒泡排序法#define M 20
#include<stdio.h>
void main()
{
int i,j,t,a[M],num;
int exchange=0;
printf("input num<%d:",M);
scanf("%d",&num);
printf("input number:");
for (i=0;i<num;i++)
scanf("%d",&a[i]);
for(i=0;i<num-1;i++)
{
exchange=0;
for(j=0;j<num-1-i;j++)
{
if(a[j]<a[j+1])
{
t=a[j];
a[j]=a[j+1];
a[j+1]=t;
exchange=1;
}
}
if(!exchange)
break;
}
printf("从大到小排序后:");
for(i=0;i<num;i++)
printf("%d",a[i]);
}

不懂

什么是降幂排序？