质因子(或质因数)在数论里是指能整除给定正整数的质数。根据算术基本定理,不考虑排列顺序的情况
下,每个正整数都能够以唯一的方式表示成它的质因数的乘积。下面求解某一个数的质因子的情况。
1. 分解为判断质数和求解因子
// 判断一个数是否为素数
private boolean isPrimer(int j)
{
if (j <= 1)
return false;
int k = (int)(Math.sqrt(j));
for (int i=2; i<=k; i++)
{
if (j % i == 0)
return false;
}
return true;
}
public String getResult(long ulDataInput)
{
long data = ulDataInput;
int i = 2;
int j = 0;
String res = "";
while (i <= ulDataInput)
{
j = i;
while (isPrimer(j) && data % j == 0)
{
res += j + " ";
data = data / j;
}
i = ++j;
}
return res;
}
2. 不必考虑是否是质数
public static void main(String[] args)
{
Main c = new Main();
Scanner sc = new Scanner(System.in);
while (sc.hasNext())
{
long input = sc.nextLong();
while (input != 1)
{
for (int i=2; i<=input; i++)
{
if (input % i == 0)
{
input /= i;
System.out.print(i + " ");
break;
}
}
}
}
}
public static void main(String[] args)
{
Main c = new Main();
Scanner sc = new Scanner(System.in);
while (sc.hasNext())
{
long input = sc.nextLong();
for (int i=2; i<=input; i++)
{
if (input % i == 0)
{
input /= i;
System.out.print(i + " ");
i = 1;
}
}
}
}
public static void main(String[] args)
{
Main c = new Main();
Scanner sc = new Scanner(System.in);
while (sc.hasNext())
{
long input = sc.nextLong();
long data = input;
for (int i=2; i<=input; i++)
{
while (input % i == 0)
{
input /= i;
System.out.print(i + " ");
}
}
if (input > 1)
System.out.print(data);
}
}
3. 递归求解
void primeFactor(int number)
{
int j = 0;
for (int i=2; i<=number; i++)
{
if (number % i == 0)
{
j = number / i;
if (j == 1)
{
System.out.print(i + " ");
return;
}
else
{
System.out.print(i + " * ");
primeFactor(j);
break;
}
}
}
}
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