Actually,
SUM = A XOR B
CARRY = A AND B
Recursive:
int add(int a, int b){
if (!a) return b;
else
return add((a & b) << 1, a ^ b);
}
Iterative
unsigned long add(unsigned long integer1, unsigned long integer2)
{
unsigned long xor, and, temp;
and = integer1 & integer2; /* Obtain the carry bits */
xor = integer1 ^ integer2; /* resulting bits */
while(and != 0 ) /* stop when carry bits are gone */
{
and <<= 1; /* shifting the carry bits one space */
temp = xor ^ and; /* hold the new xor result bits*/
and &= xor; /* clear the previous carry bits and assign the new
carry bits */
xor = temp; /* resulting bits */
}
return xor; /* final result */
On a wicked note, you can add two numbers wihtout using the + operator as follows
a - (- b)
Other way is to use ++ operator:
int a=10,b=20;
while(b--) a++;
printf("Sum is :%d",a);
Saturday, December 5, 2009
How to add two numbers without using the plus operator?
}
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