c / c ++ using time (), rand () generates a random number, generate a single random number, a random number generation a number of sequences

Problem-solving often need to use a random number, generate a lot of random numbers, in particular, ordered random number, a simple method to share about generating random numbers.

The compiler used vc6.0

① generates a random number

#include<ctime> 
#include<iostream>
using namespace std;
#define random() (rand()%x)   //定义随机值的范围 0~x 
int main(int argc, char* argv[])
{	
	cout<<rand()%100<<endl;  //输出一个100以内的随机值
	return 0;
}

The results of three continuous operation Example:



generating a random number with ctime header, the above code generates a random number for each run are the same, but the random number since there is noSet random seed;
Add code:

srand((unsigned)time(NULL)); 

#include<ctime> 
#include<iostream>
using namespace std;
#define random() (rand()%x)   //定义随机值的范围 0~x 
int main(int argc, char* argv[])
{	
	srand((unsigned)time(NULL));//设置随机数种子
	cout<<rand()%100<<" "<<endl;  //输出一个100以内的随机值
	return 0;
}

Three consecutive run Example result:

② generate large random data and the ordering

The following use of the C ++ STL containers and iterators , List doubly linked list container, for example to create 500 increments ordered random number

#include<ctime> 

#include<iostream>

#include<iomanip>

#include<list>         //list双链表容器头文件

using namespace std;

#define random() (rand()%x)   //定义随机值的范围 0~x 

int main(int argc, char* argv[])
{	
	srand((unsigned)time(NULL));//设置随机数种子
	
	list<int> a; //定义一个int型的动态数组a
	
	for(int i=0;i<500;i++)
		{
		a.push_back(rand()%10000);     //尾端插入链表
		a.sort();       //升序排序
		a.unique();//去除重复元素
		}
	
	list<int>::iterator it;  //构建一个list容器的迭代器it
	
	
	
	cout<<"-------------------------------五百个递增有序随机数---------------"<<endl;
	
	for( it = a.begin();it!=a.end();it++)
	{

		cout<<setw(4)<<*it<<" ";   //取list容器中的值输出
	
	}
	
	cout<<endl;
	
	return 0;
}

Run shot: