10/3 ==> 最接近10的数:3* 21+3* 20(divisor* 21+divisor* 20)所以商为21+20=3
class Solution {
public:
int divide(int dividend, int divisor) {
if (divisor == 0 || (dividend == INT_MIN && divisor == -1)) return INT_MAX;
long long m = abs((long long)dividend), n = abs((long long)divisor), res = 0;
int sign = ((dividend < 0) ^ (divisor < 0)) ? -1 : 1;
if (n == 1) return sign == 1 ? m : -m;
while (m >= n) {
long long t = n, p = 1;
while (m >= (t << 1)) {
t <<= 1;
p <<= 1;
}
res += p;
m -= t;
}
return sign == 1 ? res : -res;
}
};