29. Divide Two Integers

class Solution {
public:
    int divide(int dividend, int divisor) {
        if (divisor == 0 || (dividend == INT_MIN && divisor == -1)) return INT_MAX;
        long m = (dividend);
        long n = (divisor);
        m = abs(m);
        n = abs(n);
        int sign = (dividend>0)^(divisor>0)?-1:1;
        int p = n;//此处不能用int
        int q = 1;
        long ans = 0 ;
        
        
        while(m>=n){
            while(m>=(p<<1)){//如果p=1是int m=INT_MAX 那么这个循环永远无法推出
                p = p << 1;
                q = q << 1;

            }
            ans += q;
            m -= p;
            p = n;
            q = 1;
        }
        ans = sign>0?ans:-ans;
        if(ans>INT_MAX||ans<INT_MIN){
            return INT_MAX;
        }
        return ans;
    }
};