这一题最开始不会，坠吼看了一下样例，悟了

#include <iostream>
using namespace std;
int main(){int n;cin >> n;
	for (int i = 1;i * i <= n;i++)
		cout << i * i << " ";
}

有双倍经验。直接上代码：

#include<bits/stdc++.h>
#define int long long
#define INF 0x3f3f3f
using namespace std;
int n;
signed main(){
	cin>>n;
	for(int i=1;i*i<=n;i++)
		cout<<i*i<<" ";
	return 0;
}

C :

#include<stdio.h>
int a[100001];
main()
{
	int n;
	scanf("%d",&n);
	int i,j;
	for(i=1;i<=n;i++)
	{
		for(j=i;j<=n;j++)
		{
			if(j % i==0)
			{
				a[j]++;
			}
		}
	}
	for(i=1;i<=n;i++)
	{
		if(a[i]%2==1)printf("%d ",i);
	}
	return 0;
}

C++ :

#include<iostream>
#include<iomanip>
#include<cstring>
//#include<ctime>
#include<cstdio>
using namespace std;
int main()
{
	//freopen("test3.in","r",stdin);
	//freopen("test3.out","w",stdout);
	int n,i,j;
	bool a[1000000];
	memset(a,true,sizeof(a));
	cin>>n;
	for(i=2;i<=n;i++)
	  for(j=i;j<=n;j++)
	    if(j%i==0)a[j]=!a[j];
	for(i=1;i<=n;i++)
	  if(a[i]) cout<<i<<' ';
	cout<<endl;
	//printf("%0.3f",float(clock())/1000);
	return 0;
}