LintCode A + B Problem

原题链接在这里：http://www.lintcode.com/en/problem/a-b-problem/

不让用 数学运算符，就用位运算符。

a的对应位 ^ b的对应位 ^ carry 就是res中的对应位。

carry 更新为0还是1要分别讨论。

Time Complexity: O(1), 一共32位. Space: O(1).

AC Java:

 class Solution {
     /*
      * param a: The first integer
      * param b: The second integer
      * return: The sum of a and b
      */
     public int aplusb(int a, int b) {
         // write your code here, try to do it without arithmetic operators.
         int res = 0;
         int carry = 0;
         for(int i = 0; i<32; i++){
             int aCur = (a>>i) & 1;
             int bCur = (b>>i) & 1;
             res |= (aCur ^ bCur ^ carry) << i;
             if((aCur == 1 && bCur == 1) || ((aCur == 1 || bCur == 1) && carry == 1)){
                 carry = 1;
             }else{
                 carry = 0;
             }
         }
         return res;
     }
 };