leetcode:Divide Two Integers

原创于 2014-10-26 15:32:09 发布 · 347 阅读

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本文介绍了一种不使用乘法、除法和取模运算符实现整数除法的方法。通过位移操作和累加实现了对商的高效计算，并考虑了正负号的影响。

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Divide two integers without using multiplication, division and mod operator.

class Solution {
public:
    int divide(int dividend, int divisor) {
        
		bool signFlag = false;
		if ((dividend > 0 && divisor < 0) || (dividend < 0 && divisor > 0))
		{
			signFlag = true;
		}

        long long dividendInt = dividend;
        long long divisorInt  = divisor;
        
        dividendInt = abs(dividendInt);
        divisorInt  = abs(divisorInt);
		
		if (divisorInt > dividendInt)
            return 0;

        int ret = 0;
        long long remainVal = dividendInt;

        while (remainVal >= divisorInt)
        {
            long long midResult = divisorInt;
            int midRet = 1;
            
            while (midResult << 1 < remainVal)
            {
                midResult = midResult << 1;
                midRet = midRet << 1;
            }
            
            remainVal = remainVal - midResult;
            ret += midRet;
        }

		return signFlag? -ret:ret;
    }
};