[noip2006 popularity group] clear random number

notes ： The title of this topic is random.
Title Description
         I want to invite some students to do a questionnaire survey at school , For the objectivity of the experiment , He first generated... By computer N individual 1 To 1000 Random integer between （N≤100）, For the repeated numbers , Keep only one , Take out the rest of the same number , Different numbers correspond to different student numbers . And then sort the numbers from small to large , According to the order of arrangement to find students to do research . Please help Mingming finish “ duplicate removal ” And “ Sort ” The job of .
Input

Input yes 2 That's ok , The first 1 Behavior 1 A positive integer N, Represents the number of generated random numbers .

The first 2 Yes N Positive integers separated by spaces , For the resulting random number .

Output
         The output is 2 That's ok , The first 1 Behavior 1 A positive integer M, The number of different random numbers . The first 2 Behavior M Positive integers separated by spaces , Different random numbers in order from small to large .

Sample group

 Input 
10
20 40 32 67 40 20 89 300 400 15

 Output 
8
15 20 32 40 67 89 300 400

Topic ideas

        There are two approaches to this topic .

        The first approach relies mainly on the use of hash tables . The program using hash table is relatively straightforward ( Simple algorithm ), But you need to redefine the array to get from the element , And variables K To show how many elements there are . The main program written with hash table is as follows ：

int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>m;
		a[m]++;
	}
	for(int i=1;i<=1000;i++)
		if(a[i]>0) b[++k]=i;
	cout<<k<<endl;
	for(int i=1;i<=k;i++) cout<<b[i]<<' ';
    return 0;
}

        The second way of writing needs the help of STL Inside set. We can rely on set in The value of each element is unique This is used to insert when inputting , Then you can directly output the number of elements (.size()), Then use iterators (iterator) That's it . use set The main program written is as follows ：

int main()
{// There is really only input and output 
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>m;
		a.insert(m);
	}
	cout<<a.size()<<endl;
	for(it=a.begin();it!=a.end();it++) cout<<*it<<' ';
	return 0;
}

Topic scale

        The scale of this topic is as follows ：

         Hash table scale ： 

#include<bits/stdc++.h>
#define N 1005
using namespace std;
int n,a[N],m,k,b[N];
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>m;
		a[m]++;
	}
	for(int i=1;i<=1000;i++)
		if(a[i]>0) b[++k]=i;
	cout<<k<<endl;
	for(int i=1;i<=k;i++) cout<<b[i]<<' ';
    return 0;
}

STL Standard range ：         

#include<bits/stdc++.h>
using namespace std;
set<int>::iterator it;
set<int>a;int n,m;
int main()
{
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>m;
		a.insert(m);
	}
	cout<<a.size()<<endl;
	for(it=a.begin();it!=a.end();it++) cout<<*it<<' ';
	return 0;
}

There are so many questions .