【Leetcode】Divide Two Integers

Divide two integers without using multiplication, division and mod operator.

 class Solution {
 public:
     int divide(int dividend, int divisor) {
         long long a = dividend <  ? -(long long)dividend : dividend;
         long long b = divisor <  ? -(long long)divisor : divisor;
         bool sign = (dividend >=  && divisor >= ) ||
                     (dividend <=  && divisor <= );
         long long ans = ;
         while (a >= b) {
             long long c = b;
             for (int i = ; c <= a; c = c << , ++i) {
                 a -= c;
                 ans += ( << i);
             }
         }
         return sign ? ans : -ans;
     }
 };

不能用乘、除和取模，那么还可以用加、减和移位。

符号单独考虑。主要从减法出发，可以通过移位加倍被除数从而实现加速。有一点要特别注意的是可能发生溢出，需要用long long类型来进行中间的运算。