乘以7的有效方法

我们可以使用按位运算运算符将数字乘以7。首先将数字左移3位(您将获得8n)，然后从移位后的数字中减去原始数字，然后返回差值(8n – n)。
程序：

CPP

# include
 
using namespace std;
 //c++ implementation 
long multiplyBySeven(long n)
{  
    /* Note the inner bracket here. This is needed 
       because precedence of '-' operator is higher 
       than '<<' */
    return ((n<<3) - n);
}
   
/* Driver program to test above function */
int main()
{
    long n = 4;
     
    cout<

---

C

# include
 
int multiplyBySeven(unsigned int n)
{ 
    /* Note the inner bracket here. This is needed
       because precedence of '-' operator is higher
       than '<<' */
    return ((n<<3) - n);
}
 
/* Driver program to test above function */
int main()
{
    unsigned int n = 4;
    printf("%u", multiplyBySeven(n));
 
    getchar();
    return 0;
}

Java

// Java program to multiply any
// positive number to 7
 
class GFG {
     
    static int multiplyBySeven(int n)
    {
        /* Note the inner bracket here.
        This is needed because precedence
        of '-' operator is higher
        than '<<' */
        return ((n << 3) - n);
    }
     
    // Driver code
    public static void main (String arg[])
    {
        int n = 4;
         
        System.out.println(multiplyBySeven(n));
    }
}
 
// This code is contributed by Anant Agarwal.

Python

# Python program to multiply any
# positive number to 7
 
# Function to mutiply any number with 7
def multiplyBySeven(n):
 
    # Note the inner bracket here.
    # This is needed because
    # precedence of '-' operator is
    # higher than '<<'
    return ((n << 3) - n)
 
# Driver code
n = 4
print(multiplyBySeven(n))
 
# This code is contributed by Danish Raza

C#

// C# program to multiply any
// positive number to 7
using System;
 
class GFG
{
    static int multiplyBySeven(int n)
    {
        /* Note the inner bracket here. This is needed
        because precedence of '-' operator is higher
        than '<<' */
        return ((n << 3) - n);
    }
     
    // Driver code
    public static void Main ()
    {
        int n = 4;
        Console.Write(multiplyBySeven(n));
    }
}
 
// This code is contributed by Sam007

Javascript

   
function multiplyBySeven(n)
{ 
 
    /* Note the inner bracket here. This is needed
      because precedence of '-' operator is higher
      than '<<' */
 
    return ((n << 3) - n);
}
   
// Driver program to test above function
 
     n = 4;
    document.write(multiplyBySeven(n));
     
  // This code is contributed by simranarora5sos

输出：

28

时间复杂度： O(1)
空间复杂度： O(1)
注意：仅适用于正整数。
相同的概念可以用于9或其他数字的快速乘法。