CareerCup

Nice! just a few typos:

with unit test:

#include <iostream>
int add(int p, int q)
{
if(q == 0)
return p;
int k, r;
k = p ^ q;
r = p & q;
return add(k, r<<1);
}
int main() {
printf("%d\n", add(4,7));
printf("%d\n", add(401,7));
printf("%d\n", add(14,7));
printf("%d\n", add(4,47));
printf("%d\n", add(4,-97));
}

you missed the situation when q is initially 0

Use XOR instead of OR operator.

p++? i think this one uses the + operator

you should OR it with 1

This is correct solution as Initially I also didnot think of ++ operator because internally it uses + operator. But the interviewer was expecting me to use ++ operator. So, please don't go in AND & OR operations. With loop use ++ operator without loop use recursion.

'-' operation is implemented using addition & 2's complement

best solution!

{sum=a^b^(a&b)}

wrong!!!! try for 300 + 55 ...gives 319 :(

in case u dun get it lg(exp(a)*exp(b)) = lg(exp(a+b)) = a+b

Wrong Answer:

By ur logic 0+0 = 15

is this a half adder..i think we need a full adder instead ..or something for N bits like a Ripple carry adder or Carry look-ahead adders