产生随机数

#include<iostream>
#include<stdlib.h>
#include<time.h>
#include<iomanip>
using namespace std; 
int main() { 
	srand((int)time(0));  
	int a,b,c,d,e,b1,c1,d1;
	a=(rand()%20);
	if(a==0)   a++;
	b1=50-a-3;
	b=(rand()%b1);
	if(b==0)   b++;
	c1=50-a-b-2;
	c=(rand()%c1);
	if(c==0)   c++;
	d1=50-a-b-c-1;
	d=(rand()%d1);
	if(d==0)   d++;
	e=50-a-b-c-d;
	
    
	cout<<"50只动物随机分为五个组"<<endl;
	cout<<"A组"<<"  B组"<<"  C组"<<"  D组"<<"  E组"<<endl;
	cout<<setw(2)<<a<<"   "<<setw(2)<<b<<"   "<<setw(2)<<c<<"   "<<setw(2)<<d<<"   "<<setw(2)<<e<<endl;
 	system("pause");
    
    return 0;
}