数的最小除数

给定数N，找到N的最小素数。

例子：

Input: 25
Output: 5

Input: 31
Output: 31

方法：

• 检查数字是否可被2整除。
• 从i = 3迭代到sqrt(N)并跳转2。
• 如果任何数字除以N，则它是最小的素数除数。
• 如果它们都不除，则N为答案。

下面是上述算法的实现：

C++

// C++ program to count the number of
// subarrays that having 1
#include 
using namespace std;
  
// Function to find the smallest divisor
int smallestDivisor(int n)
{
    // if divisible by 2
    if (n % 2 == 0)
        return 2;
  
    // iterate from 3 to sqrt(n)
    for (int i = 3; i * i <= n; i += 2) {
        if (n % i == 0)
            return i;
    }
  
    return n;
}
  
// Driver Code
int main()
{
    int n = 31;
    cout << smallestDivisor(n);
  
    return 0;
}

Java

// Java  program to count the number of 
// subarrays that having 1 
  
import java.io.*;
  
class GFG {
// Function to find the smallest divisor 
static int smallestDivisor(int n) 
{ 
    // if divisible by 2 
    if (n % 2 == 0) 
        return 2; 
  
    // iterate from 3 to sqrt(n) 
    for (int i = 3; i * i <= n; i += 2) { 
        if (n % i == 0) 
            return i; 
    } 
  
    return n; 
} 
  
// Driver Code 
      
    public static void main (String[] args) {
      
        int n = 31; 
        System.out.println (smallestDivisor(n)); 
          
    }
}

Python3

# Python3 program to count the number 
# of subarrays that having 1
  
# Function to find the smallest divisor
def smallestDivisor(n):
  
    # if divisible by 2
    if (n % 2 == 0):
        return 2;
  
    # iterate from 3 to sqrt(n)
    i = 3; 
    while(i * i <= n):
        if (n % i == 0):
            return i;
        i += 2;
  
    return n;
  
  
# Driver Code
n = 31;
print(smallestDivisor(n));
  
# This code is contributed by mits

C#

// C# program to count the number 
// of subarrays that having 1
using System;
  
class GFG
{
      
// Function to find the
// smallest divisor 
static int smallestDivisor(int n) 
{ 
    // if divisible by 2 
    if (n % 2 == 0) 
        return 2; 
  
    // iterate from 3 to sqrt(n) 
    for (int i = 3;
             i * i <= n; i += 2) 
    { 
        if (n % i == 0) 
            return i; 
    } 
  
    return n; 
} 
  
// Driver Code 
static public void Main ()
{
    int n = 31; 
    Console.WriteLine(smallestDivisor(n)); 
}
}
  
// This code is contributed
// by Sach_Code

输出：

31

如何有效地找到直到n的所有数字的素因数?

请参考数字的最小素因数，直到n