[leetcode]Divide Two Integers

#include <iostream>
#include <vector>
#include <string>
using namespace std;

class Solution {
public:
int divide(int dividend, int divisor) {
// Start typing your C/C++ solution below
// DO NOT write int main() function

if (dividend == 0 || divisor == 0)
return 0;

int nega = 0;
if ((dividend>0&&divisor<0) || (dividend<0&&divisor>0))
nega = 1;

long long c = dividend;    //先用两个long long来存一下，不然下面abs(-2147483648)会溢出，因为正数int只能到2147483647
long long d = divisor;
long long a = abs(c);
long long b = abs(d);

if (b > a)
return 0;

long long sum = 0;
int count = 0;
int final = 0;
while (a >= b)
{
count = 1;                //a >= b保证了最少有一个count
sum = b;
while (sum + sum <= a){    //!!
sum += sum;
count += count;
}
a -= sum;
final += count;
}

if (nega)
final = 0 - final;

return final;
}
};

int main()
{
int dividend = 2147483647;
int divisor = 2;
Solution s;
cout<<s.divide(dividend, divisor)<<endl;
return 0;
}