LeetCode 29 Divide Two Integers （不使用乘法，除法，求模计算两个数的除法）

package leetcode_50;


/***
 * 
 * @author pengfei_zheng
 * 不使用乘法、除法、求模实现除法运算
 */
public class Solution29 {
    public int divide(int dividend, int divisor) {
        long result = divideLong(dividend, divisor);
        return result > Integer.MAX_VALUE ? Integer.MAX_VALUE : (int)result;
    }

    // It‘s easy to handle edge cases when
    // operate with long numbers rather than int
    public long divideLong(long dividend, long divisor) {
        
        // Remember the sign
        boolean negative = dividend < 0 != divisor < 0;
        
        // Make dividend and divisor unsign
        if (dividend < 0) dividend = -dividend;
        if (divisor < 0) divisor = -divisor;
        
        // Return if nothing to divide
        if (dividend < divisor) return 0;
        
        // Sum divisor 2, 4, 8, 16, 32 .... times
        long sum = divisor;
        long divide = 1;
        while ((sum+sum) <= dividend) {
            sum += sum;
            divide += divide;
        }
        
        // Make a recursive call for (devided-sum) and add it to the result
        return negative ? -(divide + divideLong((dividend-sum), divisor)) :
            (divide + divideLong((dividend-sum), divisor));
    }
}