include "iostream.h"
void main()
{ char *s="213142";
int a=0,b=0,c=0,d=0;
int k;
for(k=0;s[k];k++)
switch(s[k])
{ default : d++;
case '1': a++;
case '3': c++;
case '2': b++;
}
cout<<"a="<<a<<",b="<<b<<",c="<<c<<",d="<<d<<endl;
}
输出结果是多少?并说明原因