Leetcode -- 29. Divide Two Integers

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

If it is overflow, return MAX_INT.

divisor = -1, dividend = INT_MIN

INT_MAX

dividend

divisor

divisor = ±1

O(dividend)

C++代码如下：

int divide(int dividend, int divisor) {
if(divisor == -1) {
if(dividend == INT_MIN)
return INT_MAX;
else
return -dividend;
}
long long ret = 0;
int sign = 0;
if((dividend > 0 && divisor > 0) || (dividend < 0 && divisor < 0))
sign = 1;
long long x = dividend >= 0 ? dividend : -(long long)dividend;
long long y = divisor >= 0 ? divisor : -(long long)divisor;

while(x>=y)
{
long long z = y;
for(int i = 0; x >= z; i++, z <<= 1)
{
x -= z;
ret += (1 << i);
}
}
if(sign)
return ret;
else
return -ret;
}