We can multiply a number by 7 using bit wise operator. First left shift the number by 3 bits (you will get 8n) then subtract the original number from the shifted number and return the difference (8n – n).
Program:
C Programming
# include<stdio.h>
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;
}
Time Complexity: O(1)
Space Complexity: O(1)
Note: Works only for positive integers.
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