0029.Divide Two Integers

// 位运算进行除法
1029.Divide Two Integers
Return the quotient after dividing dividend by divisor.

The integer division should truncate toward zero.

Example 1:

Input: dividend = 10, divisor = 3
Output: 3
Example 2:

Input: dividend = 7, divisor = -3
Output: -2
Note:

Both dividend and divisor will be 32-bit signed integers.
The divisor will never be 0.
Assume we are dealing with an environment which could only store integers within the 32-bit signed integer range: [−231,  231 − 1]. 
For the purpose of this problem, assume that your function returns 231 − 1 when the division result overflows.
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class Solution {
public:
    int divide(int dividend, int divisor) {
        if(dividend == 1<<31 && divisor == -1) return (1<<31)-1;
        int a = divisor, b = 0;
        int f = (dividend<0) ^ (divisor<0) ? -1 : 1;
        long long dvd = labs(dividend);
        long long dvs = labs(divisor);
        int d = 0;
        while(dvd >= dvs){
            long long tmp = dvs;
            long long s = 1;
            while(dvd >= (tmp<<1)){
                tmp <<= 1;
                s <<= 1;
            }
            dvd -= tmp;
            d += s;
        }
        return f * d;
    }
};