求质数问题 希望能写出c++完整程序

[JANESTAR]

Problem description
Given a big integer number, you are required to find out whether it's a prime number.


Input
The first line contains the number of test cases T (1 <= T <= 20 ), then the following T lines each contains an integer number N (2 <= N < 254).


Output
For each test case, if N is a prime number, output a line containing the word "Prime", otherwise, output a line containing the smallest prime factor of N.


Sample Input
2
5
10

Sample Output
Prime
2

Problem Source
POJ Monthly


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[gnosis]

N (2 <= N < 254). 这么小的范围暴力都可以了
或者就线性筛素数

[高性能架构探索]

判断
n是否为质数

如果n是2，直接返回

否则
for(int i=2; i+2<sqrt(n); ++i)
if(n%i == 0)
则n不是质数
否则
做其他事

[elemusic]

这样？

#include <iostream>
#include <vector>

using namespace std;

int main()
{
	int numlines = 0;
	int num = 0;
	vector<int> vInts;
	cin>>numlines;
	if(numlines < 1 || numlines > 20)
		return -1;

	while(numlines--)
	{
		cin>>num;
		if(num < 2 || num > 253)
			return -1;
		vInts.push_back(num);
	}

	vector<int>::iterator pos;
	for(pos = vInts.begin(); pos != vInts.end(); ++pos)
	{
		for(num = 2; num < *pos; ++num)
		{
			if(*pos % num == 0){
				break;
			}
		}
		if(num == *pos)
			cout<<"Prime"<<endl<<num<<endl;
		else
			cout<<"the smallest prime factor of "<<*pos<<" is:"<<num<<endl;
	}

	return 0;
}

[elemusic]

第一个if条件写错了，应该是

if(numlines < 2 || numlines > 20)

[elemusic]

我看错了，是<1没错.....

[新铺村长]

[Quote=引用 3 楼 elemusic 的回复:]

这样？

C/C++ code

#include <iostream>
#include <vector>

using namespace std;

int main()
{
int numlines = 0;
int num = 0;
vector<int> vInts;
cin>>numlines;
if(numlines < 1 || n……
[/Quote]
感觉这样可以了

[yzl_rex]

#include <iostream>
using namespace std;

int main()
{
int case1;
cin >> case1;
if (case1 < 1 || case1 > 20)//如果你的是poj系统测试的，好像不用这个条件也可以的！你看看是否可以通过测试！
return -1;
while (case1--)
{
int N;
cin >> N;
if (N < 2 || N > 254)
return -1;
int m = N/2;
for (int j = 2; j <= m + 1; j++)
{
if (N%j == 0)
{
cout << j << endl;
break;
}
if (j > m)
{
cout << "prime" << endl;
break;
}
}
}
}

[JANESTAR]

太好了 谢谢牛人[Quote=引用 3 楼 elemusic 的回复:]

这样？

C/C++ code

#include <iostream>
#include <vector>

using namespace std;

int main()
{
int numlines = 0;
int num = 0;
vector<int> vInts;
cin>>numlines;
if(numlines < 1 || n……
[/Quote]