看看pta怎么段错误和运行超时了啊

Question

我的代码
#include<stdio.h>
#include<string.h>
int main()
{
int sum,i=0,j,cishu,n=0;
int a[999];
for(i=0; ;i++)
{
scanf("%d",&a[i]);
n++;
if(getchar()=='\n') break;
}
printf("%d\n",n);
for(j=0;j<=20;j++)
{
cishu=0;
for(i=0;i<n;i++)
{
if(j==a[i])
cishu=cishu+1;
}
printf("%d ",cishu);
}
return 0;
}

Answer 1

双循环不可取啊

#include<stdio.h>
int main()
{
    int n=0,m;
    int b[21] = {0};
    do
    {
        scanf("%d",&m);
        n++;
        b[m]++;
    }while(getchar()!='\n');
    printf("%d\n",n);
    for(int i=0;i<21;i++)
        printf("%d ",b[i]);
    
    return 0;
}