Are a and b both 32-bit integers?

• Yes.

Can I use bit operation?

• Sure you can.

Given a=1 and b=2 return 3.

Of course you can just return a + b to get accepted. But Can you challenge not do it like that?(You should not use + or any arithmetic operators.)

My Answer

Using a recursion method to solve this problem!

 1     /**
 2      * @param a: An integer
 3      * @param b: An integer
 4      * @return: The sum of a and b 
 5      */
 6     int aplusb(int a, int b) {
 7         // Recursion process
 8         if ( (a & b) == 0 ){
 9             return a ^ b;
10         } else {
11             return aplusb( (a^b), ((a&b)<<1) );
12         }
13     }

Tips

It's not the only way to get the right answer. Can you try the other way like the loop structure?