我正在尝试编写一个程序来获取输入的平方根和输入最接近的素数。我不知道在获取最近的素数时可能出现什么问题,但它没有返回正确的答案。
using System;
namespace SqrtPrime
{
class SqrtPrime
{
static void Main(string[] args)
{
int num, ctr;
Console.Write("Enter number: ");
num = int.Parse(Console.ReadLine());
int[] inp = new int[num];
for (ctr = 0; ctr < num; ctr++)
{
Console.Write("\n\nEnter number {0}: ", ctr + 1);
inp[ctr] = int.Parse(Console.ReadLine());
double sqrt = Math.Sqrt(inp[ctr]);
Console.Write("\nSquare root: {0} ", sqrt);
int cnvt = inp[ctr];
Console.Write("\nNearest prime number/s: ");
int i, Prime1 = 0, Prime2 = 0;
bool checkPrime1 = true, checkPrime2 = true;
while (checkPrime1)
{
cnvt--;
for (i = 2; i <= cnvt; i++)
{
if (cnvt % i == 0)
{
break;
}
}
if (i == cnvt)
{
checkPrime1 = false;
Prime1 = cnvt;
break;
}
}
while (checkPrime2)
{
cnvt++;
for (i = 2; i <= cnvt; i++)
{
if (cnvt % i == 0)
{
break;
}
}
if (i == cnvt)
{
Prime2 = cnvt;
checkPrime2 = false;
break;
}
}
if (Prime2 - cnvt > cnvt - Prime1)
{
Console.WriteLine(Prime1);
}
else if (Prime2 - cnvt < cnvt - Prime1)
{
Console.WriteLine(Prime2);
}
else if (Prime2 - cnvt == cnvt - Prime1)
{
Console.WriteLine(Prime1 + ", " + Prime2);
}
}
Console.ReadLine();
}
}
}
最佳答案
我建议提取方法,首先是IsPrime
public static bool IsPrime(int value) {
if (value <= 1)
return false;
else if (value % 2 == 0)
return value == 2;
int n = (int) (Math.Sqrt(value) + 0.5);
for (int i = 3; i <= n; i += 2)
if (value % i == 0)
return false;
return true;
}
然后primeBelow
和primeAbove
private static int primeBelow(double value) {
int n = (int) value;
for (int i = n; i >= 2; --i)
if (IsPrime(i))
return i;
return -1; // technical value, e.g. there's no prime below for sqrt(3)
}
private static int primeAbove(double value) {
int n = (int) value;
for (int i = n; ; ++i)
if (IsPrime(i) && (i > value))
return i;
return -1;
}
最后,NearestPrime
private static string NearestPrime(double value) {
int below = primeBelow(value);
int above = primeAbove(value);
if (below < 0)
return above.ToString();
if (Math.Abs(value - below) < Math.Abs(value - above))
return below.ToString();
else if (Math.Abs(value - below) > Math.Abs(value - above))
return above.ToString();
else
return string.Format("{0}, {1}", below, above);
}
然后使用它们
...
double sqrt = Math.Sqrt(inp[ctr]);
Console.Write("\nSquare root: {0} ", sqrt);
Console.WriteLine(NearestPrime(sqrt));
关于C# - 获取平方根和最接近的素数,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/38267632/