简易随机数发生器

代码：

/*
This is a free Program, You can modify or redistribute it under the terms of GNU
*Description: 随机数发生器,指定一个数,比如1000，要求随机产生1到1000之间的
             任意数,并且1到1000之间任何一个数产生的概率是相等的，都是1/1000
*Language: C++
*Development Environment: VC6.0
*Author: Wangzhicheng
*Date: 2012/10/5 
*/

#include <iostream>
#include <ctime>
#include <cstdlib>
using namespace std;

#define Max 1e10

typedef long  Type;

template<class Type>
class RandomProducer {
    private:
        Type *N;
        Type *random;

        
        void setN(Type num) {
            *N=num;
        }
        Type getN() const {
            return *N;
        }
        void setRandom(Type r=0) {
            *random=r;
        }
        Type getRandom() {
            return *random;
        }

        void Producer() {
            srand(unsigned(time(0)));

            Type i;
            Type k=1;

            for(i=1;i<=getN();i++) {
                if(rand()%k==0) setRandom(i);
                k++;
            }
            /*
            如果最终产生是1,那么必须保证第1次,第2次,...第N次都产生1,
            Ai={第i次产生1},i=1,2,...N.
            P(AN)=P(A1A2A3...AN)=P(A1)*P(A2|A1)*P(A3|A1A2)*...*P(AN|A1A2...AN-1)
            =1*(1/2)*(2/3)*(3/4)*...((N-1)/N)=1/N
            其余类推,所以按照以上方法,产生1到1000之间任意数的概率是1/N
            */
        }
    public:
        RandomProducer(Type num) {
            if(num<=0 || num>=Max) {
                cerr<<"输入的数据必须大于0且小于"<<Max<<endl;
                cerr<<"程序退出!"<<endl;
                exit(1);
            }

            N=new Type;
            setN(num);

            random=new Type;
            setRandom(0);

            Producer();
        }
        ~RandomProducer() {
            delete N;
            N=0;
            delete random;
            random=0;
        }

        void show() const {
            cout<<"产生的随机数是:"<<*random<<endl;
        }
};
void main() {
    cout<<"Written By Wangzhicheng,CopyRight(C) 2012/10/5  "<<endl;
    
    Type N;
    cout<<"请输入一个大于0且小于"<<Max;
    cout<<"的整数:";
    cin>>N; 
    if(!cin.good()) {
        cerr<<"输入格式非法,程序退出!"<<endl;
        exit(1);
    }
    RandomProducer<Type>instance(N);
    instance.show();
}

测试：